BLOCK 4 - coe.int · complexes. While these advances assured significant reduction in expansion of urban areas, if not compliant with the seismic environment, in a case of major seismic

NATURAL RISKS, DISASTERS AND EFFECTS

CHEMICAL ACCIDENT MANAGEMENT

PROTECTION OF CULTURAL HERITAGE

NEW TECHNOLOGIES AND RISK MANAGEMENT

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MAJEURS • MAJOR HAZARDS AGREEMENT

Conseil de l'Europe • Council of Europe

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SCHOOL OF CIVIL PROTECTION

HANDBOOK

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MAJEURS • MAJOR HAZARDS AGREEMENT

Conseil de l'Europe • Council of Europe

NATURAL RISKS,

DISASTERS AND

EFFECTS

Author

Zoran MILUTINOVICDirector, Council’s of Europe “European Center on Vulnerability of Industrial and LifelineSystems (ECILS-Skopje)”, Skopje, R. Macedonia

Head, Section for Risk and Disaster Management, Institute of Earthquake Engineering andEngineering Seismology (IZIIS – Skopje), University “St. Cyril and Methodius”, Skopje, R.Macedonia

• Professor, IZIIS - Skopje; Subjects: Engineering Seismology; Planning for Seismic RiskReduction; Aseismic Design of Life-Line Systems; Repair and Strengthening ofEngineering Structures

• Visiting Professor to Kobe University (1994), Kobe, Japan and Kyoto University (2001),Kyoto, Japan

• Author and co-author of more than 170 professional and scientific papers, reports, publications and other scientific and research materials

• Doctor of Engineering (Kyoto University, Japan, 1986)

Toute reproduction partielle ou totale à usage collectif de la présentepublication est strictement interdite sans l’autorisation expresse des auteurs.Reproduction interdite par quelque procédé que ce soit(impression, photographie, photocopie, scanner, etc.)Crédit photographique : tous droits réservés

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 The traditional disaster threat . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 New disaster threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Typology of hazards . . . . . . . . . . . . . . . . . . . . 3

3. A disaster . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.1 Major aspects of significance . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Common disaster features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 General effects of the disaster . . . . . . . . . . . . . . . . . . . . . . . . . 8

4. General characteristics of natural disasters, general counter-measures and special problem areas for emergency management . . 11

5. Effects of natural hazards on urban/regional infrastructure . . . . . . . . . . . . . . . . . . 235.1 Surface transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235.2 Airports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.3 Water supply and distribution . . . . . . . . . . . . . . . . . . . . . . . . . 255.4 Waste water collection and disposal . . . . . . . . . . . . . . . . . . . . 285.5 Solid waste collection and disposal . . . . . . . . . . . . . . . . . . . . . 305.6 Surface water drainage and flood defence . . . . . . . . . . . . . . . . 305.7 Electricity generation and distribution . . . . . . . . . . . . . . . . . . . 325.8 Gas and Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335.9 Communication systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.10 Interdependence of lifelines . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6. Effects of natural hazards on buildings . . . . . . 416.1 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416.2 Flooding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Table of contents page

NATURAL RISKS, DISASTERSAND EFFECTS

6.3 Earthquakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476.4 Snow avalanches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

7. Building typology and classification . . . . . . . . 62

8. Post-earthquake damage and usability inventory and classification . . . . . . . . . . . . . . 70

9. Human casualty and homelessness . . . . . . . . 749.1 Epidemiology of earthquake casualty . . . . . . . . . . . . . . . . . . . . 759.2 Building collapse time and evacuation . . . . . . . . . . . . . . . . . . . 799.3 Building damage and casualty . . . . . . . . . . . . . . . . . . . . . . . . . 809.4 Estimation of human casualty . . . . . . . . . . . . . . . . . . . . . . . . . 809.5 Casualties related to building collapse . . . . . . . . . . . . . . . . . . 819.6 Homelessness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

10. Building triage . . . . . . . . . . . . . . . . . . . . . . . . 8710.1 Causes of collapse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8710.2 Building construction classes . . . . . . . . . . . . . . . . . . . . . . . . . 8910.3 Structural elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8910.4 Signs of potential structural failure . . . . . . . . . . . . . . . . . . . . . 9010.5 Forms of collapses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9110.6 Search and rescue demands . . . . . . . . . . . . . . . . . . . . . . . . . . 9510.7 Survival spots for trapped victims - voids and spaces . . . . . . . . 9510.8 Triage of building collapse victims . . . . . . . . . . . . . . . . . . . . . . 96

11. Debris management and site vulnerability . . . 9811.1 Debris geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9811.2 Debris classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10011.3 Psychological issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10011.4 Environmental issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10011.5 Debris-blocking potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10011.6 Site vulnerability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

12. Some Societal and psychological issues of emergency response . . . . . . . . . . . . . . . . . . . 10812.1 Behavioural disaster myths . . . . . . . . . . . . . . . . . . . . . . . . . . . 10812.2 Disaster work and psychological trauma . . . . . . . . . . . . . . . . . 112

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1. IntroductionIn the modern world, there is an increasing paradox between the outstanding achieve-ments of science and medicine, which make life safer and healthier, and the continuingdeath and destruction associated with so-called ‘natural and technological hazards’. Theparadox is additionally complicated by the fact that science itself is not without hazard andhas led to the comparatively recent emergence of ‘man made’ threats which arise from thefailure of technological systems. People are now at risk not only from extreme geophysicalevents, such as earthquakes and floods, but also from industrial explosions, releases oftoxic substances and major traffic accidents. A growing awareness of hazards is furtherencouraged because new disasters are constantly being generated.

The significance of disaster in today’s environment sometimes comes under question. Whydo we need to bother so much? After all, disaster has been with us as long as recordedhistory, and presumably even longer. Generations of people have had to withstand disas-ter. They have suffered the consequences and recovered from them, and life has contin-ued. Basically, this is true. However, there are certain factors that need to be consideredin relation to the modern challenges that face emergency management.

1.1 The traditional disaster threatA significant reduction in what might be called the traditional disaster threat has not yet beenachieved. Most of the old problems remain, as threatening as ever. Natural phenomena suchas earthquakes, high winds including cyclones (hurricanes, typhoons) or tornadoes, volcaniceruptions, tsunamis, wildfires, floods, landslides, droughts etc. still persist. So do their basicman made counterparts, such as major accidents. These disasters continue to cause griev-ous human casualties, economic and social loss and damage to the environment.

It is certainly true that mankind has learned to cope with these problems to some extent,but they are neither eliminated nor confined. So, whilst we may have modified their effectsin various ways, they continue to inflict unacceptable pressure on a population, which, interms of total subsistence, is already finding it difficult to make ends meet.

In fact, some of the longstanding threats have grown more severe. For example, the riskfrom air disaster was insignificant in the 1920s. Few aircraft were in the air and a collisionbetween two of them would have killed only a handful people at most. Nowadays, at thebeginning of 21st century, the air risk has increased enormously. More and more aircraftfill the already overcrowded airspace of the world, especially around capital cities and inter-continental gate airports. A collision of two of them, or just a crash of one in an urban area,can amount to catastrophe. In 1977, a collision in the Azores between two passenger jetsresulted in the death of 561 people; one of these aircraft was still on the ground at the time.In 1988, a total of 270 people lost their lives following the terrorist sabotage of an airlinerover Scotland.

With some of the other longstanding threats, mankind itself has added to the risk.Increasing population alone has forced people to live in disaster-prone areas that previ-ously would not been regarded as habitable. This fact tends to apply particularly in devel-oping countries For instance, human settlements have been allowed to develop (or extend)into the flood prone areas of major river systems. Moreover, the major metropolis andmegalopolis urban areas (Tokyo, Mexico City, Los Angeles, Istanbul, and many others)continued to develop in a disaster [earthquake] prone environment, thus, adding perma-nently to their overall seismic [and other] risk potential.

What is often seen as progress can, in fact, represent a backward step. The progress ofengineering design practice, use of new (steel and/or reinforced concrete) materials in

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respect to the traditional ones (stone, sun-baked or fired brick) and new construction tech-nologies have led to construction of mid-and high-rise public and residential buildings andcomplexes. While these advances assured significant reduction in expansion of urbanareas, if not compliant with the seismic environment, in a case of major seismic event, theybecome a very lethal weapon, just as capable of killing people as any modern weapon sys-tem. Typical examples are the Spitak (Armenia, 1988), Kochaeli (Turkey, 1999) and Chi-Chi(Taiwan, 1999) earthquakes. Traditional low-rise (basement plus 1 to 2 stories) buildings,constructed with traditional materials (brick, stone or lightweight wood) posed no suchthreat. If improperly constructed their collapses have not been accompanied by heavycasualty because their size and the collapse mechanism have provided enough evacuationtime. Even if this was not the case, the low occupancy rate accounted for low mortality.

1.2 New disaster threatsNew disaster threats have developed during the 20-th century, particularly since theSecond World War. They come from what is generally termed hazardous materials or sub-stances (HAZMATs). The tragedy in Bhopal (India, 1985) ranks paramount in this catego-ry, with its estimated total of 2,500 killed and about 100,000 affected in various ways dueto the release of methyl isocyanate. But the Bhopal’s of this world (Flixborough, UK explo-sion in 1974; Seveso, Italy release of dioxin in 1976, etc.) are in many ways only the high-ly publicised tip of this particular iceberg. Hazardous materials are shifted around the trans-port systems of the world (surface, sea and air) in increasing amounts and sometimes theyare dumped in areas that are vital to the world’s future. These materials can constitute adisaster threat that is potentially comparable, if not worst, to those posed by many naturalphenomena.

The threat from atomic and nuclear sources poses yet another modern problem for emer-gency management and crisis response. The nuclear incident at Three Mile Island (USA,1979), the explosion at Chernobyl (former USSR, 1986) or uncontrolled chain reaction inthe uranium-processing nuclear fuel plant in Tokaimura (Japan, 1998) highlighted theextent of this problem. Apart from those killed and affected by radiation sickness in theChernobyl nuclear accident, some 116,000 people had to be evacuated from the area.Radioactive effects from the disaster were measured as far as 3,000 kilometres (1,600miles) and more. These peacetime nuclear accidents are likely to persist into the future ina world that increasingly searches for new and greater sources of energy.

Increased social violence has drastically affected many nations and communities.Instances of hijacking, terrorism, civil unrest and conflicts with conventional arms havebecome commonplace. These have sometimes inflicted intolerable burdens on govern-ments and societies whose existence is already precarious because of poor economic andsocial conditions. This, in turn, has produced additional strains on international assistancesources, thus diluting global counter-disaster efforts.

Whilst the threat from nuclear accidents is disturbing enough, the disaster managementproblems arising from possible nuclear war are almost beyond comprehension. The pos-sibility of global nuclear war may have receded over recent years but the possibility ofnuclear weapons being used in some lesser form of conflict cannot be disregarded alto-gether. Also, it would be unwise to rule out entirely the use of such weapons by fanaticalextremist fractions. There is the further point that if a country was not directly involved insuch nuclear conflict or terrorism, it could well suffer from the radioactive side-effects.

In sum, therefore, it can be said that new disaster threats, dominantly of man-made origin,contain some unwelcome characteristics in that they may have extremely far-rangingeffects and, at the same time, be difficult to counter.

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2. Typology of hazardsThe disaster threat, or hazard, is "any (naturally occurring or human-induced) phenome-non, process or event with the potential to cause disruption or damage (loss) to humansand their environment". In other words, it is a general source of danger.

Most of prior disaster threat classifications, or hazards, have been dominated by geo-physical processes (Table 1). It has also been usual to emphasise the impact of single ele-ments, such as wind speed or rainfall, because this is relatively easy to quantify. In prac-tice, most severe hazards arise from compound or synergistic effects, as when wind com-bines with snow to produce a blizzard or earthquakes set off landslides in steep terrain.

Alternatively, natural hazards can be divided into those of:

D endogenous earth origin (such as earthquakes and volcanic hazards)D exogenous earth origin (such as floods, droughts and avalanches)

Such physically bound classifications have limitations for disaster studies.

In order to overcome such physical bounds, a variety of factors related to damaging geo-physical events, which are not hazard-specific, were introduced:

D area extent of damage zoneD intensity of impact at a pointD duration of impact at a pointD rate of onset of the eventD predictability of the event

Rarely does a straightforward cause and effect situation apply. Hazards often consist of achain of processes and impacts leading to a disaster.

For example, let us consider the urban fires caused by gas pipes rupture due to largeground deformations in an earthquake, such as that which struck Kobe, Japan (the GreatHanshin earthquake, 1995). The primary hazard is strong ground shaking, the secondaryhazard is soil liquefaction, lateral spreads and other types of large ground deformations,and the tertiary hazard is fire.

Hazards also produce a cascade of disaster impacts ranging from biophysical to econom-ic. For example, the eruption of Mount St. Helens (USA, 1980), not only physically devas-tated an area of more than 500 square kilometres, but it also had an ordered sequence ofimpacts on forestry (ranging through thrown trees, additional production costs and reducedincome). It also had a broad impact throughout the entire Washington State, affectingrecreation, construction, retailing and insurance.

Whilst by nature the environmental hazards can be of natural or man-made origin, in termsof their appearance they may be of involuntary to voluntary character and of intense to dif-fuse impacts (Fig. 1). In general, hazards, which are increasingly man-made, tend to bemore voluntary in terms of their acceptance and more diffuse in term of impact. In contrast,natural hazards are dominantly of involuntary acceptance and are intense in term ofimpact.

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2. Hydrologic

3. Geologic

4. Biologic

I. Natural (geophysical) hazards

II. Technologic (man-made) hazards

Single event

RainFreezing rain (glaze)HailSnowWindLighteningTemperature: 'heat wave', 'cold wave', frostFog

Flooding: riverine (rain, snowmelt, natural damburst floods)Lake and sea-shore wave actionWaterloggingSea-ice and icebergsRun-off droughtGlacier advance

EarthquakesVolcanic eruptionsMass-movements: landslides, avalanches, mudflows, subsidence, etc.Silting (dykes, rivers, harbours, farmland)Shifting sands

Severe epidemics in humansSevere epidemics in plantsSevere epidemics in domestic and wild animalsAnimal and plant invasion (e.g. locusts)Forest and grassland fires

Transport accidentsIndustrial explosions and firesAccidental releases of toxic gasNuclear power plant failuresFailures of public buildings or other structuresGerm or nuclear warfare

Compound

Rain and wind storms'Glaze' stormsThunderstormsTornadic storms and tornadoesHurricanesBlizzards'White-out'Drought

Source: Modified after Hewitt and Burton (1971)

Table 1 Potentially hazardous natural and man-made phenomena and/or processes

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3. A disasterWhen the interaction between the human population and a hazard results in a loss, on asufficiently large scale, of lives, of material possessions or of what is valued by humans,the event is termed a disaster.

Two dictionary definitions for disaster are:

D Sudden or great misfortune, calamity (Concise Oxford Dictionary)D A sudden calamitous event producing great material damage, loss and distress

(Webster’s Dictionary)

Also, there are many other different definitions of disaster. Most such definitions tend toreflect the following characteristics:

• disruption to normal patterns of life, which usually is severe and may also besudden, unexpected and widespread

• human effects such as loss of life, injury hardship and adverse effect on health• effects on social structure such as destruction of or damage to government

systems, buildings, communications and essential services

Disasters are usually assessed on some quantitative criteria of death and damage. In anearly attempt at a definition of global natural disasters (Sheenan and Hewritt, 1969), a dis-aster was defined as any event that caused at least one of the following:

• at least 100 people dead• at least 100 people injured• at least US $1 million damage

This type of definition is primarily confined to losses, and provides a threshold rather thana scale. Despite its apparent precision, it has important weaknesses. While it thresholdsthe number of people that may be killed outright by an event, another, even much larger,

Fig. 1 A General spectrum of environmental hazardsfrom geophysical events to human activities

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number of deaths may result later from, for instance, disease or famine. What constitutesan ‘injury’ has never been properly defined. It is often impossible to measure economic lossaccurately. Apart from direct damage to capital goods, other, long-term [indirect] losses fre-quently exceed the direct ones. There are also great spatial differences in the wealthexposed. Consequently, a US $1 million loss can represent very different levels of impact.For example, a 1$ million loss would be caused by a much lower magnitude/higher fre-quency event in - say - Italy compared to some underdeveloped or developing country. Atthe same time, Italy would be much more likely to have the resources to recover from sucha disaster, while the same loss level might be a national catastrophe for some underde-veloped country.

More comprehensive definitions of disaster are:

D “An event, natural or man-made, sudden or progressive, which impacts with suchseverity that the affected community has to respond by taking exceptional meas-ures.” [The Asian Development Bank]

D “A serious disruption of the functioning of the society, causing widespread human,material or environmental losses which exceed the ability of the affected peopleto cope using its own resources. Disasters are often classified according to theircause viz. natural or man-made.” [The UN DHA/IDNDR, 1992]

This definition conveys a better idea of the social stress created by a disaster. Although nothreshold or scale is given, it implies a major incident requiring the mobilisation of emer-gency services.

While community loss is the major characteristic of disasters, all these definitions ignorethe fact that, in virtually every disaster, some gains also arise (Smith, 1996). Such a defi-nition is presented in Fig. 2 indicating the potential impact of environmental hazards interms of some likely losses and gains, both direct and indirect, with an indication of sometangible and intangible effects.

Fig. 2 The potential impact of environmental hazardsin terms of some likely losses and gains

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Direct effects are those first order consequences which occur immediately after an event,such as deaths, injuries and damage caused by the collapse of buildings in an earthquake.

Indirect effects emerge later and may be much more difficult to attribute directly to theevent. These include factors such as mental illness resulting from disaster shock,bereavement and evacuation.

Tangible effects are those to which it is possible to assign reasonable monetary valuessuch as the replacement or repair and strengthening of damaged property.

Intangible effects, although real, cannot be satisfactorily assessed in monetary terms.These distinctions are not entirely static. For instance, while the loss of human life hasproved notoriously difficult to assess financially in the past, as methods improve, it isbecoming a more tangible effect.

Direct losses are the most visible and spectacular consequence of disasters. They may becomparatively easy to measure, but they are not always the most significant outcome.They are caused by the immediate damage done to humans, man-made property and theenvironment.

Direct gains represent the benefits that may flow to surviving residents in the area after adisaster. These can include various forms of aid and even some longer-term enhancementof the environment (for example improvement of fertile characteristics of the agriculturalsoil by the fertile deposits of river floods or from volcanic eruption).

Indirect losses arise mainly through the second-order consequences of disasters, such asthe disruption of economic and social activities in a community. After disaster, an ‘inversetrend’ effect may occur whereby property values fall, consumers save rather than spend,business becomes less profitable and unemployment rises. These effects often outlastthose of direct losses and can be highly intangible.

Indirect gains are even less well understood. They represent the very long-term benefitsenjoyed by a community as a result of its hazard-prone location.

3.1 Major aspects of significanceIn global and/or regional terms, unless the disaster can be mitigated and managed to theoptimum extent possible, it will continue to have a dominating effect on the future.

In national terms, the impact of disaster usually results in two major setbacks:

• The direct loss of existing national assets in various forms

• The diversion of national resources and effort away from ongoing subsistenceand development in order to achieve satisfactory recovery

3.2 Common disaster featuresDespite their diverse sources, most disasters have a number of common features:

D The origin of the damaging process or event is clear and produces characteristicthreats to human life or well-being, for example, a flood causes death by drown-ing; an earthquake by building collapse

D The warning time is normally short, that is, the hazards are often known as rapid-onset events. This means that they can be unexpected even though they occurwithin a known hazard zone, such as the floodplain of a small river basin or earth-quake epicentral zone

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D Most of the direct losses, whether to life or property, are suffered instantaneously(earthquake) or fairly shortly after the event, that is, within days or weeks (highwinds, wildfires, floods, etc.)

D The exposure to hazard, or assumed risk, is largely involuntary, normally due tothe location of people in a hazardous area, for example the unplanned expansionof some cities onto unstable hill slopes or in floodplains

D The resulting disaster occurs with an intensity that justifies an emergencyresponse, that is, the provision of specialist aid to victims. The scale of responsecan vary from local to international

3.3 General effects of the disasterIn general terms, typical and the more notable social and economic consequences of dis-asters tend to be:

D loss of human life and injuryD panic; social disruption (e.g. no sense of community, security or control)D increase in the likelihood of social unrest or violent conflictD damage to the natural resource base and to the environmentD loss of housing; temporary and/or permanent migrationD loss of industrial and/or agricultural production (hence employment, income and

tax revenue)D damage to infrastructure (including transportation and communications systems)D disordered markets and distribution; loss of commerceD immediate downgrading and degradation of living conditions owing to the deferral

or cancellation of other development plans that deal with real social needsD short-term reduction in GDP and per capita incomeD imbalances in the fiscal budget as a result of emergency relocations of expenditureD immediate and medium-term inflatory pressure due to market disorders and exter-

nally financed reconstruction expenditure

Most, if not all of the above consequences could be expected from disasters caused by allthe types of adverse natural and man-made phenomena as listed in Table 1.

Natural hazard events have both immediate and longer-term effects upon people, physicalstructures and economic activities (Table 2). These effects are ‘generic’ to all natural haz-ards considered in this module, although their extent and nature will vary according to theparticular hazard and the particular physical characteristics of the area affected.

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Table 2 Potential primary and secondary effects of natural hazards

Social or human effects Economic effectsPhysical effects

Fatalities

Injuries

Loss of income oremployment opportunities

Homelessness

Disruption of businessdue to damage to buildings

Damage to industrialplants and equipment

Loss of productive workforce, through fatalities,injuries, and relief efforts

Disruption of communica-tions networks

Costs of response andrelief

Ground deformation andloss of ground quality

Collapse of and structural damage tobuildings and infrastructure

Non-structural damage tobuildings and infrastructure (e.g. component damage)

Disease or permanentdisability

Psychological impact ofinjury, bereavement,shock

Loss of social cohesiondue to disruption of community

Political unrest wheregovernment responseperceived as inadequate

Costs of repair, rehabilitation, medicaland welfare assistance

Loss of confidence byinvestors, withdrawal ofinvestment

Loss of markets andtrade opportunities,through short-term business interruption

Losses borne by theinsurance industry, weakening the insurance market and increasing premiums

Progressive deteriorationof damaged buildingsand infrastructure whichare not repaired

Secondary

Primary

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Table 3 The main activities of the cycle of emergency management

ActivitiesProcess

MitigationMeasures that reduce orminimize the effects ofdisasters on a community

• an initial assessment of hazard, vulnerability and risk

• the elaboration of a detailed long-term strategy and plan, in which some ele-ments can be swiftly implemented and others would require lead-time andresources. These elements include engineering and construction of hazard-resistant and protective structures and infrastructure

• land-use planning

• Institutional measures to engender the political will and expertise to ensure mit-igation and measures to establish a “culture of safety” through public awarenessof risk

• economic measures to ensure diversification, and encouragement of wide-spread insurance

ResponseSaving life, protectingproperty and dealing withimmediate damage anddisruption

• implementation of emergency/disaster reaction plans

• activation of the counter-disaster system

• search and rescue

• provision of emergency food, shelter, medical assistance; survey and assessment

• evacuation measures

• protection of property against looting

ReconstructionLong-term replacement ofdestroyed buildings andinfrastructure

• Introduction of improved building systems and programmes

• Utilisation of international disaster assistance to optimum effect

• implementation of disaster experience in future research and development programmes

• ensuring that development is planned to ameliorate the impact of subsequentdisasters

RecoveryAssisting communities’return to a normal level offunctioning. Includes res-toration and rehabilitation

• restoration of essential services

• restoration of repairable buildings and installations

• provision of temporary housing

• assistance to the physical and psychological rehabilitation of sufferers

• designation of key individuals to act as focal points for the formulation and imple-mentation of preparedness activities including “emergency officers’” in govern-ment institutions and the community

• formulation of up-to-date plans for rapid response

• special provisions for emergency action such as evacuation to safe areas; pro-viding warning systems and emergency communications

• institutionalisation of public education and training programmes

• categorisation and upgrading of facilities and equipment for search, rescue andemergency treatment of victims

PreparednessPlans for response bynational, regional andmunicipal governments,organisations, communi-ties and individuals

Source: The Institution of Civil Engineers (1995), “Megacities – Reducing Vulnerability to Natural Disasters”

Disaster Event

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4. General characteristics of natural disasters, general counter-measures and special problem areas for emergency managementThe emergency management process, in the broader meaning of the term, means contin-uous implementation of actions before a disaster to reduce the effects of natural hazardswhen they occur. The term ‘emergency management process’ applies to a wide range ofpolicies and measures that can be instigated; from physical and procedural ones (such as:the construction of stronger buildings, or the application of standard techniques for incor-porating hazard assessment in land-use planning), to effective preparedness and readi-ness, both responsible for planning of effective and efficient response by national, region-al and municipal governments, organisations, communities and individuals (Table 3).

Natural disasters are part of the environment in which we live. They do not discriminatebetween people or countries. And yet, no disaster is entirely natural. Human activity invari-ably aggravates the risk through insufficient attention to where and how settlements arebuilt or natural resources exploited. Disasters are, therefore, complex events; and theproblem of disaster prevention and mitigation has many facets.

In each country and in each region, the types of natural hazards faced are different. Somecountries are prone to floods, others have histories of cyclone damage, and others areknown to be in earthquake regions. Most countries are prone to some combination of var-ious natural hazards and all face the possibility of technological disasters as industrialdevelopment continues. The effects these environmental hazards are likely to have and thedamage they are likely to inflict depends largely on what is present in the region affected:the people, their houses and the infrastructure. Each country is different. For any particu-lar location or country it is, therefore, critical to know the hazards likely to be encountered.

The understanding of natural hazards involves comprehension of:

D the physical mechanism of destructionD causes of how hazards ariseD sources, probability of occurrence and magnitudeD the consequences of impactD the elements that are most vulnerable to their effects

Many techniques are known for disaster mitigation, and their relevance to the countriesthat need them most is now clear. However, the ‘epidemiology’ of disasters – the system-atic science of what happens in a disaster – shows that they are largely preventable. Thereare many ways to reduce the impact of a disaster and to mitigate the effects of a possiblehazard or accident.

While the characteristics, nature and extent of effects will vary according to the particularnatural hazard and the particular physical characteristics of the area affected, most coun-termeasures and special problem areas for emergency management, as detailed inTables 4, are somehow ‘generic’.

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Table 4 General characteristics of disasters, general countermeasures and specialproblem areas for emergency management

EARTHQUAKES

Characteristics

• Usually no warning, Following a major earthquake, secondary shocks may give warning ofa further earthquake

• Onset is sudden• Earthquake-prone areas are generally well identified and well known• Major effects arise mainly from violent ground movement (vibration), fracture or slippage;

especially they include damage (usually very severe) to structures and lifeline systems,plus considerable casualty due to lack of warning

General countermeasures

• Development of possible warning indicators• Land-use regulations• Building regulations• Relocation of communities• Public awareness and education programmes

Special problem areas for emergency management

• Severe and extensive damage, creating the need for urgent countermeasures, especiallysearch and rescue, and medical assistance

• Difficulty of access and movement• Widespread loss of or damage to infrastructure, essential services and life support sys-

tems• Recovery requirements (e.g. restoration and rebuilding) may be very extensive and costly• Rarity of occurrence in some areas may cause problems for economies of countermea-

sures and public awareness• Response problems may be severe, extensive and difficult (e.g. rescue from a high occu-

pancy building collapses, or in a circumstances where additionally a chemical or radiationhazard exists, etc.)

• Victim identification may often be very difficult

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Table 4 General characteristics of disasters, general countermeasures and specialproblem areas for emergency management /continued-1/

VOLCANIC ERUPTION

Characteristics

• Volcanoes, which are likely to constitute a disaster threat, are internationally well docu-mented and, in many cases, monitored for possible activity. Usually, the major eruptionscan therefore be predicted

• Volcanic blast can destroy structures and environmental surrounds, and also cause fires,possibly including forest fires

• Land-surface cracking may affect buildings and other structures• Lava flow can bury building and crops. It may also cause fires and render land unusable• Ash, in its airborne form, can affect aircraft by ingestion into engines• Ground deposit of ash may destroy crops and also affect landuse and water supplies• Ash may also cause respiratory problems• Mudflows may arise from associated heavy rain


• Land-use regulations• Lava control systems• Development of monitoring and warning systems• Evacuation plans and arrangements• Relocation of population• Public awareness and education programmes


• Access during eruption• Timely and accurate evacuation decision(s)• Public apathy, especially if there is a history of false alarms or small eruptions. Thus, it may

be difficult to maintain public awareness and also to implement evacuation plans• Control of incoming sightseers when evacuation programmes are being implemented

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TSUNAMI (Seismic Sea Wave)

Characteristics



• Timely dissemination of warning, in view of the possible short period between receipt ofwarning and the arrival of the tsunami wave

• Effective evacuation time-scale• Search and rescue• Recovery may be extensive and costly due to severe destruction and damage

• The velocity of the wave depends of the depth of water at the point where the seismic dis-turbance occurs. Initial wave velocity may be as high as 900 kph (560 mph), slowing toapproximately 50 kph (31 mph) as the wave strikes the shoreline

• Warning time depends on distance from point of wave origin• Speed of onset varies• Impact on shoreline can be preceded by marked recession of normal water level prior to

arrival of wave. This can amount to a massive outgoing tide, followed by the incomingtsunami wave. People may be trapped by going to investigate the phenomenon of the out-going tide and then being struck by the incoming wave

• The tsunami wave can be very destructive; wave heights of 30 metres have been known• Impact can cause: flooding, salt-water contamination of crops, soil and water supplies; also

destruction of, or damage to buildings, structures and shoreline vegetation

• Optimum arrangements for receipt and dissemination of warning• Evacuation of threatened communities from sea level/low land level areas to high ground,

if sufficient warning available• Land-use regulations (but these are likely to be difficult to implement if tsunami risk is per-

ceived as rare)• Public awareness and education programmes

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TROPICAL CYCLONE (Typhoon, Hurricane)

Characteristics



• Assessment of effects and needs may be difficult, especially due to bad weather followingmain disaster impact and to problems of access and movement caused by high damagelevels

• Destruction or loss of emergency resources (e.g. transport, emergency food and medicalsupplies, shelter material) may be widespread

• Difficulty of access and movement in caring out urgent relief operations, especially emer-gency feeding, shelter and medical assistance programmes

• Search and rescue• Widespread destruction/disruption of essential services• Evacuation• Rehabilitation of agriculture (especially tree crops)

• Usually long warning, derived from systematic international meteorological observation(include remote sensing)

• Speed of onset gradual• Tends to conform to seasonal pattern• Major effects arise mainly from destructive wind force, storm surge and flooding from

intense rainfall. Landslides may follow, flooding and heavy rainfall• Destruction and/or severe damage may be caused to buildings and other structures, roads,

essential services, crops and the environment generally. Major loss of life and livestockmay occur

• Effective warning arrangements• Precautionary measures during warning period (e.g. boarding-up buildings, closing public

facilities)• Moving people to safe shelters• General readiness and clean-up measures prior to expected cyclone season (or extreme

windstorm event) to reduce risk of flying objects• Building regulations• Public awareness and education programmes

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FLOODING

Characteristics



• Difficulties of access and movement• Rescue• Medical and health difficulties e.g. arising from sanitation problems)• Evacuation• Loss of relief supplies• Large-scale relief may be required until next crop harvest

• Long, short or no warning, depending on type of flood (e.g. flooding within parts of a majorriver system may develop over a number of days or even weeks, whereas flash floods maygive no usable warning)

• Speed of onset may be gradual or sudden• There may be seasonal patterns to flooding• Major effects arise mainly from inundation and erosion; specifically, they may include iso-

lation of communities or areas, and involve the need for large-scale evacuation

• Flood control (e.g. by walls, gates, dams, dykes, levees)• Land-use regulations• Building regulations• Forecasting, monitoring and warning system(s)• Relocation of population• Evacuation plans and arrangements• Emergency equipment, facilities and materials, such as special flood boats, sandbags,

supplies of sand (plus designated volunteers for implementation of emergency measures)• Public awareness and education programmes

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LANDSLIDING

Characteristics



• Difficult of access and movement in affected areas• Search and rescue• Risk of follow-up landslides may hamper response operations• Relocation (as distinct from temporary evacuation) may be resisted by indigenous com-

munities• Rehabilitation and recovery may be complex and costly• In severe cases it may not be possible and/or cost-effective to rehabilitate the area for

organised human settlement

• Warning period may vary. Little or no warning may be available if the cause is earthquake;however, some warning may be assumed in the case of landslides arising from continuousheavy rain. Minor initial landslips may give warning that heavy landslides are to follow.Natural movement of land surface can be monitored, thus providing long warning of futurepossibility of landslides

• Speed of onset is mostly rapid• Damage to structures and system can be severe (building may be buried or villages swept

away)• Rivers may be blocked, causing flooding• Crops may be affected. Sometimes areas of crop-producing land may be lost altogether

(e.g. in the major slippage of surface soils from a mountainside)• When landslides are combined with very heavy rain and flooding, the movement of debris

(e.g. remains of buildings, uprooted) may cause high levels of damage and destruction

• Land-use regulations and building regulations• Monitoring systems where applicable• Evacuation and/or relocation of communities. Relocation has proved successful where

crop-growing land areas have been lost• Public awareness and education programmes

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WILDFIRES (or BUSHFIRES)

Characteristics



• Maintenance of adequate community awareness and preparedness• The arsonist problem is difficult to counter• Establishment and maintenance of adequate fire-fighting resources, especially if the threat

is spasmodic• Establishment of an adequate warning system, particularly the meaning of signals (e.g.

sirens) and their interpretation by threatened communities• Timely dissemination of warning and, if applicable, decision to evacuate• Long-term recovery may be prolonged, due to high levels of environmental damage and

destruction• Evacuation movement, either out of affected areas, or to safe havens within such areas

• Most wildfire-prone areas are well known and well defined• Wildfire threat tends to be seasonal• Speed onset may vary. It can be rapid under conditions of high temperatures and high

wind, when major fire fronts advance very fast. Fragments of fire from a main front may becarried forward by the wind, starting new fires further ahead. This is sometimes known as‘spotting’

• Effects can be very destructive, especially in loss of buildings, timber and livestock (andhuman life if emergency arrangements are inadequate)

• Recovery from effects on the environment may take several years• Evacuation of communities may be difficult and dangerous in the face of a major fire front

• Accurate risk assessment• Effective monitoring and warning systems (including remote sensing, to define ‘curing’ or

drying-out of vegetation)• Fire prevention regulations• Seasonal mitigation measures (e.g. fuel reduction)• Building regulations• Public awareness and education programmes, especially to ensure that individuals, fami-

lies and communities co-operate in the application of measures for prevention and mitiga-tion, and especially that they maintain adequate standards of preparedness during thehigh-risk season

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DROUGHT

Characteristics



• Response requirements (e.g. feeding programmes) may be extensive and prolonged, thusinvolving major commitment and expenditure of resources

• Prolonged drought may undermine self-reliance of affected communities, thus making itdifficult to withdraw emergency management assistance

• Logistic requirements may exceed in-country capability, particularly if large external (inter-national) input commodities are involved

• Major areas liable to drought are usually well known• Periods of drought can be prolonged• Area(s) affected may be very large• Long warning• Effects on agriculture, livestock, rural industry production and human habitation may be

severe. This may lead to prolonged food shortages or famine• Long-term effects can be in the form of severe economic loss, erosion that affects future

habitation and production, and sometimes abandonment of large tracts of land• Man-made activities may aggravate the possibility and extent of the drought problem (e.g.

over-grazing of agricultural land, destruction of forests or similar areas)• The inability and/or unwillingness of the population to move from drought-prone areas may

exacerbate the problem

• There are few, if any, quick and easy solutions to the drought problem; effective counter-measures tend to be mostly long term

• The long-term resolution of drought problems usually rests with national governments andinvolves major policy decisions

• Since these decisions involve human settlement, they are often sensitive and difficult ones.• International cooperation and assistances usually plays an important role in coping with

major drought problems• Land management and special plans (e.g. for irrigation)• Response to drought-caused emergencies usually includes provision of food and water

supply, medical and health assistances (including monitoring of sanitation and possibilityof epidemic), emergency accommodation (maybe on an organized camp or similar basis)

• Information programmes, especially to assist aspects such as land management

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EPIDEMICS

Characteristics



• Loss of medical and health resources (e.g. clinics, medical supplies) during disaster impact(e.g. by earthquake or flood) may inhabit response capability

• In country shortage of special equipment (e.g. water-purifying equipment and installations)• Integration of external (international) medical and health assistance with local systems• Containment and control of common diseases (e.g. enteritis and diarrhoea) that can have

a mass effect, especially if relevant medical and health resources are severely limited

• Disaster-related epidemic arises from the disrupted living conditions that follow disasterimpact

• Epidemic may arise from: food sources; water sources; inadequate medical and healthfacilities/standards; malnutrition; vector-borne sources (e.g. mosquitoes); etc.

• Types of disease include: hepatitis; typhoid; diphtheria; malaria; cholera; influenza; enteri-tis; diarrhoea; skin diseases; food poisoning; etc.

• Under post-impact conditions, when personnel and facilities may be limited, outbreaks mayprove difficult to contain and control. This may practically apply if community health edu-cation is sub-standard

• Warning (i.e. risk) is self-evident in most post-impact circumstances• Speed of onset is mostly rapid

• An effective medical and health sub-plan, within the overall local or area (region) emer-gency management plan. This medical and health plan needs particularly to cover pre-paredness measures and the capability to deal with post-emergency eventualities

• Close post-emergency monitoring of medical and health aspects• Reinforcement of medical resources and supplies in anticipation of epidemic outbreak• Public awareness and education, booth before and after disaster impact

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MAJOR ACCIDENTS

Characteristics



• Unexpected nature of accidents may pose problems of reaction and response time• Response problems may be severe, extensive and difficult (e.g. rescue from a building col-

lapse, or in a circumstances where a chemical or radiation hazard exists, or where thereare multiple casualties such as in major rail accident)

• Victim identification may be difficult in some cases

• Usually violent in nature (e.g. industrial or other explosions, aircraft crash, major fire, traincollision)

• Can have limited or widespread effect (e.g. an aircraft crash may affect only those onboard, whereas an explosion involving hazardous chemicals may affect a wide area ofpopulation)

• Mostly limited or no warning, though there may be longer warning of effects of, say, leak-age of chemical, oil spill, etc.

• Speed of onset usually rapid

• Good physical planning (e.g. siting of potentially accident-prone buildings or complexes).• Special building regulations, if applicable• Good in-house safety and management standards/procedures, including evacuation plans

and periodic tests)• Effective organisation of local (on-site) emergency services (e.g. fire services and rescue

teams) which are available to take immediate response action prior to the arrival of publicemergency services (fire brigades, specialized rescue teams, first aid teams and civil pro-tection)

• Effective community or area (region) emergency plans, so that co-coordinated responsecan be achieved

• Training in handling effects of specific hazards

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Table 4 General characteristics of disasters, general countermeasures and specialproblem areas for emergency management /concluded/

CIVIL UNREST

Characteristics



• Overloading of resource organisations (e.g. medical authorities, welfare agencies, essen-tial services) due to demands of civil unrest incidents, in addition to normal commitments

• Difficulty of integrating ‘peacetime’ resource organisations (which are non-combatant innature) with ‘military-type’ operations, which are necessary to deal with violent civil unrest

• Usually the responsibility of police, paramilitary and armed forces. However, other emer-gency services such as fire services, medical authorities and welfare agencies becomeinvolved

• Violent and disruptive activities occur (e.g. bombing, armed clashes, mob demonstrationand violence)

• Patterns of civil unrest are difficult to predict. Therefore, effective warning may also be dif-ficult

• In many civil unrest circumstances, especially terrorism, the instigators have the initiative,thus complicating the task of law enforcement authorities

• Firm application of law and order regulations and requirements• Imposition of special emergency measures and regulations (e.g. restricted movement, cur-

fews, security checks)• Positive information programmes aimed at maintaining majority public support for govern-

ment action against disruptive elements/factions

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5. Effects of natural hazards on urban/regional infrastructureInfrastructure is the physical fabric of society. It is the basic framework necessary for thewell-being and productive development of a modern industrial society. It plays a vital rolein economic and social development, and ultimately, in providing improved standards of liv-ing for the population.

The various elements of the physical infrastructure are often described as lifelines,because they are so essential to all human activities. This description is particularly appro-priate in the context of disaster mitigation. In the aftermath of disaster, infrastructure playsa crucial role in emergency operations, and in sustaining the functions of any urban area.

In many urban areas the development processes often do not function effectively and can-not keep pace with the rate of urban growth. This leads to:

D development occurring on unsuitable land which is often hazard-prone, such asflood plains, watershed areas, and unstable slopes

D buildings being constructed and occupied with little or no supporting physicalinfrastructure systems

D inadequate economic opportunities and social facilities for the population; etc.

Infrastructure may be considered in three broad groups:

D transport systems (roads, railways, airports, port facilities)D utilities (water, waste-water /sewerage/, surface water drainage /atmospheric

water discharge/solid waste, electricity, gas and oil, etc.)D communications

The vulnerability of infrastructure is specific, depending on the type of hazard.

5.1 Surface transportSystem: The components of a surface transport systems which may be affected by natu-ral hazards include different types of bridges (by structural system and construction mate-rial) tunnels, overpasses, embankments and cuttings, road pavement, drainage systems,overhead signs, electricity and telephone cables. Typical additional components of rail-ways system are tracks, portals, accompanied signalisation and stations.

The surface transport system often provides the primary means of transportation within theregion and urban areas. Larger towns and cities act as focal points for regional and nation-al transport networks, and external highways and railways are essential to maintain theselinks.

To allow routine activities to continue and to guarantee passage for emergency servicesand mass relief operations, the road network requires special attention in risk assessmentand mitigation planning.

Post-event importance: Highways and the regional road system are crucial for supplyingsome types of fuel, food and possibly water for the operation of emergency services, fortransport of heavy equipment and machinery for massive search and rescue and debrisremoval operations, as well as transport of shelter and other relief supplies.

To be usable, surface transportation systems (roads and railways) need functioning sur-face water drainage systems, communications and, in case of railways, a power supply. Inregular and emergency conditions, as well, they must be kept free of obstructions of alltypes.

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Natural hazard Road/highway component ConsequencesEffects

Table 5 Potential effects of natural hazards on components of the surfacetransport systems

High winds

Storm surge

Heavy rain

Earthquake

Landslide

Volcano

Earthquake

Floods

Overhead signs, electricityand telephone cablesSuspension and cable-stay bridges

UnderpassesEmbankments and bridgesCuttings Roads at grade

Underpass BridgesRoads at grade

Embankments

Cuttings

Drainage systems

Embankments

Bridges and flyovers

Tunnels

Roads at grade

Embankment Roads at grade

Tunnels

At grade Operation

TrackPortals Stations and tunnels

Tunnels and underground railways

Blown over

Flooded Scoured or washedawayLandslip Temporarily flooded

Flooded Scour at foundations Temporarily flooded, culverts washed Liquefaction, landslide, washout Liquefaction, landslide Scour damage, collapse

Settlement, foundation failureand liquefaction

Failure of abutment,failure of columns, displacement ofdeck

Portal failure, Lining failure Ground failure andliquefaction

Ground failureGround failure, buryingPortal blocked

Dust and lahar coverVery low visibility

DistortionCollapse Fire

Flooded

Highway restrictedElectricity failureRestricted use

Closed to trafficClosed to traffic

Closed to trafficTemporarily closed

Closed to trafficClosed to trafficTemporarily closed,roads severedRoad closed

Road closed

Road closed

Closed to traffic

Closed to traffic

Closed to traffic

Partially or com-pletely closed

Closed to trafficClosed to traffic

Closed to traffic

Traffic restrictedTraffic restricted

Closed, no serviceClosed, no serviceClosed, no service

Closed, no service

Additional vulnerability of railways

Source: The Institution of Civil Engineers (1995), "Megacities - Reducing Vulnerability to Natural Disasters"

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Vulnerability of the system: Damage to a small part of a surface transportation system(for example a collapsed bridge or culvert or a washed-out road) can effectively isolatelarge areas or prevent movement, thus emergency and/or relief operation, within the cityor between the city and its hinterland. Similarly, a localised failure in the railway networkcould cause enormous damage to the local and national economy.

Vulnerability of the population: People will suffer from direct effects of the disruption oftransport and from secondary effects such as lack of access for emergency services and/orrelief supplies. Rural or semi rural communities can be particularly vulnerable. As accessto these areas is often limited even in normal circumstances, they may easily be isolatedafter a disaster.

5.2 AirportsSystem: A modern airport contains a wide range of facilities, including runways, taxiwaysand aprons, passenger terminals, carparks, offices, hotels, cargo sheds, aeroplane repairand maintenance hangers, oil storage tanks, power station, water treatment plant, sewagetreatment plant, garages for emergency vehicles, highways and rapid transit systems.

The role of airports in facilitating international and domestic passenger and freight trans-port is particularly important to the national and local economy. Its role is particularly sig-nificant because each region or large city generally has access to one airport.

Post-event importance: Hazards impacts are unlikely to result in the closure of a majorairport for more than a few days, with the exception of landslides and earthquakes whichcould cause substantial damage requiring closure for a longer period of time. Airports areusually the primary means of international access, and are therefore essential in the pro-vision of emergency aid after a natural/man-made disaster.

Vulnerability: Damage to runways is relatively easily and quickly reparable. However, therepair of associated facilities, if severely damaged, will take some time to make an airportoperational. The disruption of airport facilities can result in substantial economic losses. Ifdamage results in airport inoperability, some of the functions can be carried out by small-er (sport) airports or military airfields.

Airports usually operate independently of the electricity and water supplies. However, theyrely on surface transport and on the operation of specialised equipment and the telecom-munications network. A list of some potential natural hazard effects on airport facilities ispresented in Table 6.

5.3 Water supply and distributionSystem: The components of water supply and distribution systems may include dams andreservoirs, well fields, desalination plants, river off-take works, transmission mains, aque-ducts, canals, treatment works, service reservoirs, pumping stations, distribution and sup-ply mains.

Post-event importance: An adequate supply of clean drinking water is vital for all com-munities in normal as well as in emergency conditions. Interruption of water supplies canbe tolerated for a short time, as many people have become accustomed to routine short-ages and interruptions. A lack of clean water for more than a few hours, however, threat-ens public health and health risks are increased if sanitation systems break down.Protection of water supply systems is therefore of the highest priority. Emergency suppliesneed to be made available within hours and the system must returned to normal operationwithin days.

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Natural hazard Component ConsequencesEffects

Table 6 Potential effects of natural hazards on airports

High winds

Storm surge

Heavy rain

Earthquake

Landslide

Volcano

Snow

Operations

Cargo sheds Terminals and other buildings PlanesMasts and cables

Operations

Runway, aprons and taxi ways Cargo sheds and hangars Terminals and other buildings Unsurfaced areas

Operations

Runway, taxi way and aprons Drainage systems

Runway, taxiway and aprons Buildings

Building contents, equipment Oil storage

Runway, taxiway and aprons


Operations

Sensitive equipment

Operation


Dangerous flyingconditionsRoofs torn off Roofs torn off

Damaged Blown down

Flooded

Debris

Flooded

Flooded

Washout

Temporarily flooded Temporarily flooded Damage, blockage

Ground failure andcrackingPartial collapse, firesCollapse and damage, firesPartial collapse, fires

Partial collapse orcovered with debris

Covered in dust

Partial collapse dueto weight of dustVery low visibility,engine failureDamaged by dust

Poor visibility andobstruction Covered in snow

Partial collapse fromweight of snow

Temporary shutdownLoss of cargo Loss of business

Loss of serviceElectricity supplyand communica-tions failure

Temporary shutdownRestricted operation Loss of cargo

Loss of business

Restricted operation

Temporary shutdownRestricted operation Extended period of flooding

Restricted or nooperation Restricted or nooperation Loss of service

Pollution

Restricted operation

Restricted operation Reduced services

Temporary shutdownRestricted operation

Temporary shutdownTemporary shutdownRestricted service


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Water supplies are essential for hospitals and emergency facilities to function. After anearthquake, water for fire fighting is needed immediately. This need not be of potable qual-ity, and any local source of fresh, salt or standing water can be used. Where no other suit-able sources exist, storage within the distribution system can be used, even if means ofreplenishment are temporarily disrupted. For this, distribution systems with service reser-voirs, which have significant storage distributed by gravity are more useful than those inwhich water is pumped directly into the system.


Table 7 Potential effects of natural hazards on water supply systems

High winds

Storm surge

Heavy rain

Earthquake

Landslide

Volcano

Reservoirs

Overhead cables

Treatment worksPumping stations

Reservoirs RiversRiver off-take Treatment works Pumping stations

Reservoirs

Ground-water

Transmission mains, aqueducts, canalsTreatment works

Service reservoirs Pumping stations below and above groundDistribution system

Reservoirs

River off-take RiversTransmission mains, aqueducts, canalsService reservoirs Treatment works, pumping stations

Reservoirs Aqueducts, canals

Wave surcharge,overtopping of damsBlown down

Flooded Flooded

Overtopping of damsRiverine floodsScourFlooding Flooding

Structural failureof dams

Liquefaction ofdeposits Line fracture

Damaged

Damaged Damaged

Pipe fracture

Overtopping or failure of dams

River diversion High sedimentFracture by groundmovement Damaged Damaged by groundmovement

Pollution by dustPollution and sediments from lahar


Scour downstream,endangered damsPower and telecomsfailure

Close down Close down

Possible dam failureDifficult treatmentLoss of sourceClose down Close down

Loss of supply,flooding damagedownstreamFracture of wells,supply failureSupply cut

Loss of operation,reduced output,close downLoss of storage Lost or reducedcapacityBurst, increasedleakage throughpipes, loss of storage

Loss of supply,flooding damagedownstream Loss of sourceTurbiditySupply cut

Loss of storage Lost or reducedcapacity

Difficult treatmentBlockage and supply failure

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Vulnerability of the system: Most hazard events are unlikely to result in serious damageto water supply systems (Table 7) and it should be possible to restore services within days.Significant loss of life is also unlikely, although repair costs could be high. In the past, land-slides and lahar flows have caused disasters by precipitating dam failure or overtopping,but it is earthquakes which are most likely to cause the greatest damage to water supplysystems. Possible effects of an earthquake include failure of dams, severe damage totreatment works and multiple fractures of pipelines. Secondary effects may include wide-spread flooding and a shortage of water for fire fighting, resulting in further damage.Flooding is more likely to result from small appenditure failures preventing the closure ofvalves than from a dam failure.

The provision of water supplies depends on a reliable electricity supply for operation of con-trols and pumping. Although alternative arrangements for supply can be used in an emer-gency, they are of limited value unless they can continue to operate for several weeks.

Vulnerability of the population: Any hazard event (Table 1) can disrupt the water supply,and may create public health problems, particularly if the source of supply is remote fromthe city. The supply may become polluted with the consequent risk of widespread sickness.Public awareness of basic hygiene precautions and the need to purify water will help toreduce these risks.

5.4 Waste water collection and disposalSystem: The components of a waste-water collection and disposal system which may beaffected by natural hazards include the sewerage network and manholes, pumping sta-tions, submarine outfalls and sewage treatment works and disposal facilities, together withtheir associated electrical and mechanical equipment (Table 8). Some installations operatewithout mechanical plant and septic tanks and cesspools are in widespread use.

Vulnerability of the system: After the installation of a wastewater collection and dispos-al system, the population and the city become increasingly dependent on it, because othermeans of disposal are abandoned.

The system becomes increasingly vulnerable as more sophisticated equipment is installed.The operation of waste-water collection and disposal systems with mechanical plantdepends on reliable electricity supplies and on telemetry systems and surface waterdrainage systems; failure of the latter and the resultant flooding will affect the seweragesystem. Outfalls can be damaged by sea/lake surge and river scour.

The disposal of sludge from treatment works may depend on road access or marine/lakeloading facilities.

Earthquakes are likely to cause most damage to a system, damaging seriously or destroy-ing treatment works and pumping stations and causing multiple pipe fractures.

Vulnerability of the population: A sewage treatment system is essential to prevent thespread of disease by direct contact with untreated sewage or by pollution of drinking water.Failure of the system can defeat that objective by polluting the city, contaminating drinkingwater and perhaps causing long-term environmental and ecological damage.

Primary and secondary damage effects: Failure of a particular pumping station could createlocalised problems such as sewage flooding of streets and houses. A general electrical fail-ure affecting all pumping stations could create extensive flooding of sewage. Failure of sys-tems which accept untreated sewage from hospitals and industrial areas will create addi-tional hazards from the spread of bacteria and toxins. A severe outbreak of disease after ahazard event would adversely affect the population and have subsequent social and eco-nomic effects which would delay recovery from the event.

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Table 8 Potential effects of natural hazards on waste-water facilities


High winds

Storm surge

Heavy rains

Earthquake

Landslide

Volcano

Reservoirs, lagoons

Overhead cablesSludge disposals facilitiesTreatment works

Reservoirs, lagoons

Treatment plant

Road access Sewerage system Pumping stations

Sludge disposal facilitiesSea outfall

Road access Reservoirs, lagoonsCollection systems River outfall

Collection system

Pumping stations

Treatment works

Reservoir, lagoons

Collection system, rising mains andcanalsTreatment works,pumping stations Reservoirs, lagoons

Reservoirs, lagoonsCollection system

Treatment works

Overtopping of retainingstructures Blown downShut down

Damaged laboratories, stores

Retaining structuresbreached Destroyed

Damaged, out of useFlooded Flooded

Flooded

Fractured

Damaged, destroyedOvertopping Flooded Failure by scour

Multiple fractures:Manholes damagedchange of gradients by liquefaction Damage from ground fail-ure and tilting by groundmotion and liquefactionDamage, damage to roadaccess

Base, wall and embankment failure byliquefaction

Fracture by ground movement

Failure by ground movement Failure by ground movement

Pollution by dust Blockage by dust and ash

Process failure due todust and ash

Progressive failure

Loss of power Sludge disposal halted

Operations inhibited

System failure and pollutionSystem failure and pollutionSludge disposal haltedSewage in streets Surface ponding ofsewage Sludge disposal halted

Inshore pollution

Sludge disposal haltedProgressive failure Escape of raw sewageLocal flooding

Polluted groundwater,spillage of sewage

Systems failure and pollution

Systems failure and pollution, sludge disposalhalted Systems failure and pollution

Polluted ground-water,spillage of sewage

Systems failure and pollution Systems failure and pollution

Reduced efficiency Local flooding and pollutionBacteriological pollution ofreceiving water

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5.5 Solid waste collection and disposalSystem: Disposal of waste may involve landfill, incineration, composting or recyclingreusable waste. Recent developments in solid waste management focus on reducing thevolume of waste, or `waste minimisation’.

A solid waste disposal system is necessary to maintain standards of hygiene to minimisethe spread of disease, and to discourage illegal disposal methods. Although a hazardevent is unlikely to have a very serious effect on waste disposal, disruption of the systemwould compound social, economic, drainage and health problems (Table 9).

Vulnerability of the system: The solid waste disposal system depends on supplies of fuelfor collection vehicles and for disposal sites, and on efficient transport networks. An effi-cient system reduces the risk of surface water drainage systems being blocked by wasteand of potential health problems.

5.6 Surface water drainage and flood defenceSystem: The provision of surface water drainage facilities is often neglected during rapidand unplanned development. Pressure for urban land often leaves little space for water-ways, and buildings encroach on areas which should be kept clear for drainage purposes.When an urban area expands, more ground is covered by impermeable surfaces and rain-fall run-off is increased. The risk of flooding is thereby increased if the additional run-off is


Table 9 Potential effects of natural hazards on solid waste disposal systems

High winds

Stormsurge/tsunami

Heavy rain

Earthquake

Landslide

Volcano

Snow

Vehicles

Disposal sites

Disposal sites

Highways

Landfill

Highways Landfill disposal sitesIncinerator disposal sites

Highways

Disposal sites

Highways

Highways

Stop operation

Blown debris

Flood

Restricted access

Increased leachate

Restricted access Fracture of membrane Damaged by groundmovement

Restricted access

Disturbed by ground failure

Access restricted by lahar flow

Restricted access


Streets polluted bydumped refuse Local contamination

Ground and waterpollution

Ground and waterpollutionPossible ground andwater pollution

Refuse pollutionGroundwater pollution Systems failure

Ground and waterpollutionSystems failure



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not catered for in a properly designed drainage system (Table 10). Systems need to beplanned and designed as internal parts of the city’s development and installed before thebuilding development takes place. All components of the system retain sediment, whichneeds regular clearance if the structures are to be effective over the mid- to long-term.

Vulnerability of the system: The efficient functioning of a surface water drainage systemcan be disrupted in a number of ways. For example, pipes, culverts and channels can beblocked by debris, including uncollected refuse, they can fail by bursting or scouring underexcessive surcharge; watercourses can overflow or their training walls and embankmentscan fail; and a power failure will de-activate pumps.

The overflow of streams is the most common cause of inland flooding and the most vul-nerable areas are the floodplains. In large urban areas, floodplains tend to be areas inwhich much of the development is concentrated and, therefore, large parts of the built-upareas can be affected.


Table 10 Potential effects of natural hazards on storm water drainage and flooddefence systems

High winds

Sea surge/Tsunami

Heavy rain

Earthquake

Landslide

Volcano

Lakes, balancing ponds

Pumping stations

River levees

Sea walls

Channels, pipes culverts

River levees

Rivers

Channels, pipes culvertsPumping stations below ground Pumping stations above ground

Embankments and levees

Pumping stations Rivers


Rivers


Surge, waves

Flooded, damaged

Breached, overtoppedBreached, overtopped

Blocked with debris,burst

Breached, overtopped High levels, banksovertopped

Fractured, scouredDamage fromground failure Damage fromground motion, andliquefaction Damage fromground failure

DamagedBlocked

Fractured by groundmovement

Blocked with lahar

Blocked with ashand lahar


Overtopping andflooding

Local flooding,water pollutionFlooding of city

Flooding of city

Surcharged andflooding, water pol-lutionFlooding of city

Flooding of city

Local flooding,water pollutionLocal flooding,water pollutionLocal flooding,water pollution

Flooding of city,water pollution

Local floodingFlooding of city,water pollutionFlooding of city,water pollution

Flooding of city,water pollutionLocal flooding,water pollution

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Sea surges generated by extreme winds combined with low pressure and heavy rainfall ortsunami waves can cause flooding in coastal cities, especially those, which have expand-ed onto coastal, swamp areas. Land subsidence, caused for example, by the abstractionof oil or water, drainage of wetlands, or mining and rising sea-levels relative to the land mayincrease the frequency of risk of coastal flooding.

The likely extent and depth of flooding, covered either by rainfall, storm surge or dambreak, can be estimated. Meteorological records and water level and rainfall infiltration canbe used for flood warning purposes and tide data for operational warning of sea flooding.Models are available for predicting flooding by a dam break. The risks of overtopping, orfailure of river levees, embankments and coastal defences designed to offer protectionfrom floods require special design attention, because the consequences of failure could bemore destructive than the effects of flooding without embankments. A warning system andevacuation plans are essential.

5.7 Electricity generation and distributionSystem: The components of a power supply system which may be affected by a naturalhazard include power stations (thermal, geothermal, hydroelectric, nuclear), transmissionlines, main and distribution substations, and distribution systems (aboveground-overheadand underground) (Table 11). Power stations may be within or near a city but are oftenremote.

Post-event importance: Electricity supplies are essential for many critical facilities in post-disaster situations, including hospitals, water-pumping stations, media, and street lighting.Strategic facilities often possess alternative power supplies, but these are usually intend-ed to cover brief interruptions in the main supply and therefore have limited fuel reserves.Prolonged disruption of the mains supply would stretch the capacity of alternative supplies,and may cause extensive health and economic damage.

A prolonged breakdown in electricity supplies would disrupt economic, political and com-mercial activities, and would restrain long-term local and national economic development.However, many urban areas already experience acute shortage in supply because of insuf-ficient capacity and the provision of electricity may be delayed for several years after thecompletion and occupation of buildings.

Vulnerability of the system: Power generation depends on supplies of primary fuels andon the communications network. Electricity supplies are, therefore, at risk not only fromdirect effects of hazard events, but also from indirect effects. A reliable supply of electrici-ty is, in turn, essential to the water supply, gas supply, telecommunications network, trans-port systems, to hospitals, industry and commerce.

Transmission line towers designed to withstand extreme winds may resist the groundmotion generated by some earthquakes, but liquefaction may cause foundation failure.The risk of failure at generating stations will depend on construction quality, design fea-tures and equipment types, such as use of rigid bases which are frequently shown to besusceptible to failure.

Vulnerability of the population: Where electricity supplies are routinely interrupted orinadequate, the population will have adjusted to this situation, and may therefore be lessinconvenienced by possible disruptions caused by hazard events. However, increasingprosperity raises aspirations and increases demand for electricity, and disruptions to thesupply may then appear more significant. Informal settlements rarely have access to mainspower supplies, but some will make illegal and dangerous connections to the mains net-work, while others will install small generators.

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5.8 Gas and OilSystem: Gas supplies within an urban area may be of:

• natural gas, delivered through high-pressure transmission mains and low-pressure distribution mains

• town gas derived from oil• coal or liquefied petroleum gas delivered in bottled form or by tanker to on-site

storage.

Other fuels, such as fuel oil and kerosene are also stored and distributed in urban areas.


Table 11 Potential effects of natural hazards on electricity generation and distribution

High winds

Sea surge

Heavy rain

Earthquake

Landslide

Volcano

Transmission towers and lines Generating stations, cooling towers, substationsDistribution lines (overhead)

Generating stations, other facilities Distribution cables (underground)

Reservoirs

Generating stations, otherfacilities

Dams

Generating stations, substations, other facilities

Distribution lines (overhead)

Dams

Generating stations, otherfacilities Transmission lines

Transmission lines

Collapse

Damage and partialcollapse Collapse

Equipment flooded

Flooded

Overtopping of dams

Flooded

Damage fromground failure andmotionDamage fromground failure andmotion, e.g. isola-tors, equipment sup-port framesCollapse of lines andpole mountedtransformers

Failure from overtopping Failure by groundmovementFailure by groundmovement

Swept away by lahar flows andshort-circuited byash deposits


Loss of supply

Loss of supply

Loss of supply

Shut down

Loss of supply

Possible progressive failureLoss of supply

Loss of supply

Loss of supply

Local loss of supply

Loss of supply

Loss of supply

Loss of supply

Loss of supply

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System safety – design: To ensure the safety of a gas system and reduce its vulnerabil-ity to hazard events requires high standards of design, installation and maintenance.Systems which have developed over many years, with a mixture of old and new pipelinesand equipment, require special attention. Control of pressure and gas flow are key ele-ments of the network and must include designed-in safety features.

There are many other aspects related to gas network design, and reference should bemade to the appropriate technical data to ensure that the network is fit for the purpose.

According to the location, various measures are used to mitigate the risk to gas mainswhich cross faults. In rural areas, the main will be supported on trestles above ground,allowing relative movement between the pipe and the ground. However, where pipes aretrenched across a fault, the preferred solution is for the buried pipeline to cross at rightangles, with the depth of burial minimised and the trench backfilled with light and prefer-ably granulated material. In this situation, the main must be straight for a distance of atleast 200 metres on either side of the fault. The ground movement will then put the pipe intension and not compression. An increase in wall thickness is also recommended for mainswhich cross fault lines.

System safety – operations: Safe operation of gas networks is the first priority of gassuppliers. If designed, installed and maintained in accordance with best practice, day-to-day control of the system is likely to be from a control centre facility, using communicationequipment to monitor and control the system. Clear operating instructions to all personnelworking on the system are essential. Guidelines are also important for non-specialist per-sonnel working in the vicinity of gas installations. Gas suppliers should ensure that employ-ees and contractors are trained to the level of competence necessary to safely completeroutine tasks.

System safety – emergency procedures: It is good practice to prepare for all anticipat-ed incidents by the provision of written emergency procedures. These must be producedby competent qualified people, suited to local circumstances, and tested regularly by prac-tice drills with all people involved, both directly and indirectly. Regular in-depth training andbriefing on emergency procedures should be given to all personnel.

Most modern industrial appliances are designed to shut off automatically in response to thedrop in pressure that a major leakage would cause. Seismic shut-off valves can provideadditional protection in earthquake-prone areas.

The restoration of services can take time because of the need for safety checks, but thisdelay allows leaks to be repaired, pipes to be purged of air, and gas pressure to build up.Numerous small leaks, which do not trigger automatic shut off, give more cause for con-cern. Although identification and repair of fractures is still needed, safety depends much onthe awareness of individual customers.

Vulnerability of the system: There are various components in a gas-supply system whichare vulnerable to natural hazards, i.e., well fields, processing plant, pumping and boosterstations, transmission mains, storage tanks and bottled-gas stores, regulator stations, dis-tribution mains and house connections (Table 12).

Distribution of gas and oil relies on the provision of a supply main from the supply fields orport, and on transport facilities for conveying fuel to energy transfer works. Electricity is need-ed to operate gas pumps and control valves, and a communications network is needed tooperate monitoring and control systems. Oil supply lines to refineries and depots, from portsand between facilities, although not dispersed across the city, could also be vulnerable.

Gas and oil infrastructure must be designed with a built-in safety system, as secondaryhazards such as fire or explosion followed by fire could be catastrophic. Even under nor-

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mal conditions, distribution networks can be regularly fractured in numerous locations dueto subsidence or other interference.

Actions in an emergency: Emergency procedures will define levels of emergencies andresponse needed. For example, in a major emergency, initial action will probably requirean assessment by a senior competent person, and the establishment of an emergencycontrol centre is usually the first step in a major emergency affecting a large area. Thelocation of control centres should be identified and specified in local and national emer-gency plans, and officers-in-charge nominated, who will ensure that the emergency pro-cedures are followed. Communication is vital, particularly with gas company personnel andemergency services.

In some emergencies, people will need to be evacuated before the integrity of the systemcan be secured. The make-safe and restoration phases of emergency procedures arecomprehensive and detailed, and must be followed precisely. The person in charge will useemergency procedures and personnel judgement to manage the emergency to a safe con-clusion.


Table 12 Potential effects of natural hazards on gas and oil transport infrastructure

High winds

Sea surge

Heavy rain

Earthquake

Landslide

Volcano

Offshore rigs

Offshore rigs

Coastal refineries, tank farmbunds and other facilities

Refineries and otherfacilities

Transmission and distribution system

Refineries and other facilities

Offshore rigs

Tank farms

Transmission and distribution systemRefineries and other facilities

Transmission and distribution systemRefineries and other facilities

Damage to rigs

Damage to substructureDamage from flooding

Damage fromflooding

Fractures fromground motion andfailureDamage fromground motion andfailure Damage fromground motion andfailure Damage fromground motion andfailure

Fractures fromground movementDamage fromground movement

Damage from laharflows Damage from ashand fumes


Restricted supplysuperstructure

Loss of supply, pollutionLoss of supply

Loss of supply

Explosions, leakage, fire

Explosions, leakage, fire

Explosions,leakage, fire

Explosions,leakage, fire, loss ofsupply, pollution

Loss of supply, pollutionExplosions, leakage, fire

Loss of supply, pollutionRestricted operation

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5.9 Communication systemsSystem: The range of communications systems available has increased rapidly in recentyears, and includes telephone systems, cellular radiotelephone systems, private radionetworks (both corporate and amateur), radio repeater systems in the VHF/UHF bandsand the Internet (Tables 13 and 14).

Communications systems consist of a limited number of principal components includingtelephone exchanges (central offices), microwave radio equipment, communication tow-ers, and above ground and/or underground distribution cables. The functions of principalcomponents are:

• Remote line units (concentrators) - small units (capacity: 200 to 2000 lines) towhich subscriber lines are connected, typically with limited stand-alone capac-ity, which are normally connected to a local exchange for wide-area connec-tion, but can interconnect calls between its subscribers if connection to thelocal exchange is cut.

• Local exchanges (processors) - provide processing power and wide-area inter-connection capability for concentrators; each serves typically 10 to 20 con-centrators.

• Tandem exchanges - used to switch telephone traffic between exchanges toreduce individual routes between local exchanges; not directly connected tocustomer lines.

• Toll (trunk) exchanges - used to connect long distance calls betweenexchanges - similar function to tandem exchanges.

• Trunk routes - long-distance connections between trunks exchanges.• Junction routes - shorter distance connections between local exchanges. • Network diversity - ability of the network to route calls over physically different

paths, separated by geography, by transmission media or a combination.• Network management - ability to control flow of telephone traffic in a network

by a combination of expansive and restrictive controls. Expansive controlsallow more options for routing calls through a diverse network to enable trafficto bypass an area of damage. Restrictive controls reduce the number of callsentering or leaving a point in the network to the level that the network canaccommodate.

• VHF and UHF radio - systems operating over a short distance (line of sight) notusually capable of connection into public telephone systems.

• Cellular radiotelephone - connected via radio links to transmitters/receiverswith permanent connections to public telephone systems, offer full telephoneaccess, including international calls. Instruments can be used from any cell (anarea covered by a transmitter/receiver) operated by the company, and alterfrequencies automatically if the instrument moves from one cell to another dur-ing a conversation.

Post-event importance: Telecommunications networks depend on a reliable supply ofelectricity. Every other component of the infrastructure depends on reliable communica-tions and a hazard event will generate excessive demands on the system. This issueneeds to be specifically addressed in all emergency plans.

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Vulnerability of the system: The vulnerability of a network is concentrated within a fewcritical areas:

• the supply of electricity to central offices for operation of exchanges · potentialdamage to telephone exchanges due to their location

• local reticulation, using copper conductors• cabling between exchanges using fibre-optic cables


Table 13 Potential effects of natural hazards on communication systems

High winds

Earthquake

Heavy rain

Storm surge

Volcano

Radio and TV towers

Overhead cables

Radio and TV towers

Overhead cables

Underground cables

Telephone exchanges

Radio and TV towers

Underground cablesTelephone exchanges

Radio and TV towers

Overhead cables

Underground cablesTelephone exchanges

Telephone exchanges

Disorientation ofaerials

Collapse

Collapse of poles Severing of cable

Damage/collapse

Collapse of polessevering of cablesMinor quake:little damage Major quake:severed cables andbroken ducts Minor quake: dislocation of printedcircuit boardsMajor quake: collapse of building

Interference with signal path FloodedFlooded

Flooding and majordamage

Flood damage toradio equipment Collapse of poles,severing of cables FloodingFlooding and majordamage

Failure of air conditioning due to dustLahar flow damage


Disruption to or loss of transmissioncapability Complete loss oftransmission High fault rateLoss of service

Complete loss oftransmission High fault rate, loss of service High fault rate

Complete loss ofservice

Temporary loss ofservice

Long-term loss ofservice

Temporary loss ofservice High fault rateComplete loss ofservice Long-term completeloss of service

Complete loss oftransmission Loss of service

High fault rateComplete loss ofservice

Temporary servicedisruption

Long-term completeloss of service

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• ducts and cables entering buildings in areas subject to ground movement • the misalignment of aerial systems for microwave radio• unbraced equipment• insufficient spare parts• flooding of basement and ground floor equipment, etc.

Component Vulnerability Mitigation


Table 14 Reducing the vulnerability of communication components

Remote lineunits (concentrators)

Localexchanges

Tandemexchanges

Toll (trunk) exchanges

Trunk routes

Junction routes

Network management

Cellular radiotelephone

Loss of powerFlooding

Isolation from processor


Earthquake


Earthquake


Earthquake

Cable routes affected byland dislocationCollapse of polesRadio routes affected bystrong winds

As above

Loss of powerLoss of connection toexchanges

Loss of connection to fixednetwork

Standby powerCareful site selection, provision of splicing roomabove ground, dual cable vault pumpsSeparated links to processor

Standby powerCareful site selection, provision of splicing roomabove ground, dual cable vault pumpsAnti-earthquake braces for equipment

Standby powerCareful site selection, provision of splicing roomabove ground, dual cable vault pumpsExtensive interconnection with other TandemsUse of network managementAnti-earthquake braces for equipment

Standby power, dual power, grid sourceCareful site selection, provision of splicing roomabove ground, dual cable vault pumpsExtensive interconnection with other TandemsUse of network managementAnti-earthquake braces for equipment

Diverse routing

Deepen setting of cable polesDiverse routing

As above

Standby power, dual power, grid sourceAlternative emergency routing

Alternative emergency routing

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5.10 Interdependence of lifelinesThe elements of the infrastructure network, or lifelines, depend on each other in varyingways and to varying extents. Failure of one element may lead to failure or disruption of oth-ers. This is known as ‘cascade effect’.

The lifeline interdepencence is ilustrated in Table 15; where (5) indicates high, (3) moder-ate, (1) low and (-) none lifeline interdependence.

Following a hazard event it woud be of vital importance to restore (Table 15) water andelectricity supplies, telecommunications, transport and fuel supplies, as well as restore tomaximum extent the operations capability of the health care system.

It would be neither economical nor practical to protect every lifeline system as well as alllifeline system components against extremly rare events. For this, adequate preparednessand response plans should be elaborated by each lifeline/utility operator and agency incharge, and adequate maintainance and incident reaction teams trained accordingly.

Following a hazard event, the objective of all lifeline and utility operators should be torestore full services in the shortest possible time. A co-ordinated plan for restoration of allservices is required in order to increase the effectiveness of the restoration as well as toavoid/minimise the adverse impacts.

For example, restoring the water supply system will be ineffective without adequaterestoration of electricity supply. On the other hand, restoring electricity supply, without theproper immobilisation of the gas system may cause fires or even explosions at the gas-leak locations, as was extensively recorded in the post-disaster aftermath of the GreatHanshin (Kobe) Earthquake of 1995 when the electric supply system was put in operation.

Lifelines interdependence chart is presented in Fig. 3. The chart indicates the possible sec-tors where the principal operations support of local/central emergency services and agen-cies might be needed additionally to the regular maintenance and incident reaction capa-bility of lifeline/utility operators. These sectors are outlined by areas (Fig. 3) where the life-

Fig. 3 Interdependence of lifelines

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line support line is considerably higher than the lifeline dependence line. The lifeline/utilitysystems on the left hand side from the first intersection point are relatively independent of,and supportive of, the lifeline/utility systems placed on its right hand side; and thereforeshould be, by all available means, restored in the shortest possible period after a hazardevent.

Table 15 Interdependence of lifelines /Adapted from Lifelines in Earthquakes, CAE, University of Canterbury, New Zealand/

Support Lifeline

Dependent lifeline

Wat

er S

uppl

y

Fuel

Sup

ply

Elec

trici

ty S

uppl

y

Heal

th

Food

Sup

ply

Road

s/Hi

ghw

ays

Tele

com

Ser

vices

Stor

m D

rain

age

Sani

tary

Dra

inag

e

Railw

ays

Build

ing

Serv

ices

Fire

-figh

ting

Build

ings

Med

ia

Ports

Airp

orts

Gas

and

oil s

uppl

y

Tota

l dep

ende

nce

1. Water Supply

2. Fuel Supply

3. Electricity Supply

4. Health

5. Food Supply

6. Roads/Highways

7. Telecom Services

8. Storm Drainage

9. Sanitary Drainage

10. Railways

11. Building Services

12. Fire-fighting

13. Buildings

14. Media

15. Ports

16. Airports

17. Gas and oil supply

Total importance

- 5 5 5 5 3 5 3 5 - - - - - - - - 36

5 - 5 5 5 5 5 - - 5 - - - - 5 - - 40

5 5 - 5 5 5 5 - - 5 - - - 3 5 - - 43

5 5 5 - 5 5 5 3 5 - 5 3 5 5 - 3 - 59

5 5 5 5 - 5 3 3 5 5 5 3 5 3 5 3 5 70

5 3 3 5 5 - 3 5 - - - - - 3 - - - 32

5 5 5 5 5 5 - 1 - - - - - - - - - 31

5 3 3 1 1 3 - - 5 - - - - - - - - 21

5 5 5 5 5 3 3 5 - - - - - - - - - 36

5 5 5 5 5 5 5 3 - - - - - 3 3 - - 44

5 3 5 - - 1 - - 5 - - - - - - - 5 24

5 5 1 5 5 5 3 1 - - 3 - - 3 3 - - 39

- 3 5 5 5 5 5 5 - - 5 5 - - - - - 43

5 5 5 5 5 3 5 - - 3 5 - 5 - - 5 - 51

3 5 3 3 3 5 5 3 3 5 - 5 5 - - - - 48

3 5 3 3 3 5 5 5 3 3 5 5 5 5 - - - 58

5 3 5 5 5 3 5 - - 3 - 5 - - 3 - - 42

71 70 68 67 67 66 62 37 31 29 28 26 25 25 24 11 10 -

The lifeline interdepencence index:(5) indicates high(3) moderate(1) low(-) none lifeline interdependence

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6. Effects of natural hazards on buildings6.1 Wind

6.1.1 Mechanism of destructionMechanism of destruction includes pressure and suction from wind, buffeting for hours ata time. Strong wind loads imposed on a structure may cause it collapse, particularly aftermany cycles of load reversals. More common damage is to building and non-structural ele-ments (roof sheets, cladding, chimneys) blown loose. Wind-borne debris causes damageand injury. High winds cause stormy seas that sink shipping and pound shorelines.Extreme low air pressure at the centre of a tornado is very destructive and houses mayexplode on contact.

6.1.2 Wind ForcesA typical wind speed record is shown in Fig. 4. The mean wind over the record can be rep-resented by a steady force and the turbulent portion, that is, a portion of a fluctuatingdynamic force.

The frequency spectrum of the dynamic portion is such that only a small range of struc-tures is affected by it and design is customarily carried out based on static forces derivedfrom a peak gust speed. Structures likely to experience wind-induced vibration are light-weight, slender forms with low structural damping such as suspension and cable-stayedbridges, guyed masts, tall chimneys and towers. Vibrations arise from turbulence in thewind flow or instabilities developed in the airflow around the structure which can give riseto vibrations at right angles to or in line with the direction of the wind.

Wind forces are proportional to the square of the wind speed so that, for example, a 20%increase in wind speed from 100 to 120 km/h represents a 44% increase in wind force.

Forces exerted on buildings vary according to the shape of the building and the wind ori-entation, and can be either (Fig. 5):

D pressuresD suctions

Fig. 4 Wind speed record over 1024 seconds period

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Some of the concentrations ofhigh wind pressures ondwelling houses (Fig. 6) arecaused by the formation of vor-tices where the wind flows overedges and corners.

6.1.3 Wind damageThe greatest source of winddamage to buildings, especiallydwellings, is to roofs and thegreatest source of damage toroofs is uplift forces (Figs. 5 and8). Wind forces on roofs andwalls are heavily dependent onthe overall form of the building.

The shape of the building,especially that of the roof, willinfluence the magnitude of thewind loads on the structure.The higher the wind loading,the greater is the tendency forthe building to suffer wind dam-age. Experience and experi-ment have shown that houseswith hip roofs have the bestrecord of resistance. The next best roof shape is the high gable roof with a pitch of 30-45°.The low gable roof and flat roofs have been found to have the worst record of resistanceto wind loads (Gibbs and Browne, 1982). Some good and bad features of building form onwind forces are illustrated in Fig. 7.

Gables and overhangs are especially vulnerable, and designs which avoid these, such ashipped roofs and clipped eaves, perform well in high winds. Shade, for windows can stillbe provided by individual canopies which may be damaged by high winds, but without lossof integrity to the building as a whole.

Light-sheeted roofs are especially vulnerable; their weight is insufficient to counterbalanceeven the forces due to moderate winds so that the survival of the roof structure is depend-ent on its being tied down to a large enough mass to stop it becoming air-borne. Indwellings this can often mean providing steel reinforcement from roof plate level down tothe foundations.

Roof sheeting is commonly a major source of damage from wind. Failure of roof or moreparticularly side sheeting on buildings can greatly increase the forces exerted on the wholestructure by the wind. The opening created by the failure (Fig. 8) allows the wind into thebuilding, creating an internal outward pressure which adds to the suction and uplift forcesalready acting.

Suction is particularly important in shed-type buildings such as factories and warehouses.In this case it is aggravated by the failure of shutter doors (in particular those of a rollertype) which are rarely designed to withstand appropriate wind forces. Shed-type structuresare particularly vulnerable to high winds and considerable care is required in ensuring thatthe wind resisting system is consistent as a whole for any wind direction, and that mem-bers (eaves ties, for example) liable to go into compression are designed to do so. Small

Fig. 5 Schematic illustration of pressure and suction wind forces

Fig. 6 Areas of high suction pressuresdue to wind

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dwellings, especially in hot climates, areoften of very light construction with timber-framed walls and partitions, and light-sheet-ed roofs. These frequently have little or noanchorage to the ground and can be rolledover, reducing them to debris.

High wind pressures may also damageunreinforced masonry walls especiallywhere they contain openings or are only par-tially supported. Freestanding non-rein-forced masonry is particularly liable to failureby toppling.

Tanks and silos are often not anchored to afoundation. When empty or partially full theybecome liable to toppling by the wind. Thereis a possible prior action, that is, to fill thetank or silo before the windstorm arrives.(For earthquakes, paradoxically, they are attheir most vulnerable when full.)

High winds can generate missiles from build-ing debris, rocks, pebbles, coconuts andloose timber, for example, and these make asubstantial contribution to the damage,especially to glass. Flying steel or aluminiumroof sheets are a particular threat to life andproperty and can travel great distances.Missiles are of particular concern in torna-does where quite heavy objects can bedrawn up in the low-pressure vortex andtransported for considerable distances.

Glass is vulnerable both to wind pressureand to the impact of wind-borne missiles.Dynamic effects on glass are of particularconcern near corners of high buildings. Indwellings glass can be protected by the useof shutters.

It is important that buildings and structures, and the possible inflicted damages, are seenin the context of the whole disaster in any scenario of wind post-disaster performance. Thisrequires consideration of thestructure in a post-windstormenvironment where servicesmay be non-functional. Over-head power and telephonelines may be blown down ordestroyed by falling trees andlandslides. Buried services –water, gas, power and tele-phone – may be damaged bylandslides and flooding. Accessby road or rail may be impossi-

Fig. 8 The effects of an opening in theupwind face

Fig. 7 Wind forces on the principalexternal building elements(roofs and walls

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ble due to landslides, fallen trees and damaged bridges. Major bridges may be wind dam-aged. Lesser bridges may be destroyed, blocked by river-borne debris or isolated by ero-sion of riverbanks.

The implications to buildings are that, in the post-windstorm environment:

• building services and communications may not be operating• maintenance services may not be available for days, weeks or even months• broken windows and leaking roofs will continue to let in the rain• lifts, air conditioning and heating may be out of action• small defects may be the source of major loss from water damage• minor damage may render the building unusable, etc.

6.1.4 Main mitigation strategiesThese include:

D design and construction of structures to withstand wind forcesD wind load requirements in building codesD wind safety requirements for non-structural elementsD good construction practices and strong fixingsD micro-climatic siting of key facilities, such as, in lee of hillsidesD planting of wind-breaks, planning of forestry areas upwind of townsD provision of wind-safety buildings for community shelter in vulnerable settlements

6.2 Flooding

6.2.1 Mechanism of destructionThese include:

D inundation and flow of water with mechanical pressures of rapidly flowing waterD currents of moving or turbulent water can knock down and drown people and

animals in relatively shallow depthsD debris carried by the water is also destructive and injuriousD mud, oil and other pollutants carried by the water can ruin crops and building

contentsD flooding destroys sewage systems, pollutes water supply and may spread diseaseD saturation of soils may cause landslides or ground failure

6.2.2 Flood forcesGrowing human vulnerability to flood events should give significant cause for concern.Floods cause many deaths and much damage, but their structural effects are not usefullyconsidered alongside those caused by wind and earthquake since, leaving aside tsunamis,the additional forces caused are not dynamic in nature. In engineering buildings, the prin-cipal effects are more likely to be foundation failure, although more general failures will becaused in non-engineering domestic (traditional) buildings. In other words, floods thataffect a building for many hours, even days, will alter the load-path of the ever-presentgravity loads. Expensive foundation treatment, such as tying together isolated footings, orthe use of piles and deep raft foundations is only possible for the most important buildings.

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Experience shows that the type of material used for construction of a building can have aconsiderable impact on the damage inflicted by water. Structures built with concrete willencounter much less physical damage than structures built with wood. In the case of a con-crete structure situated on an erosion-prone bank, the foundations can be affected byundercutting, leading to partial or total collapse. Brickwork is more vulnerable to the effectsof flood than reinforced concrete, as it can suffer cracking from even small movement in abuilding’s foundations and from its high absorbency.

Regarding tsunamis or tidal waves, caused by earthquake or wind, there is a dynamiceffect introducing horizontal loads applied to the surface of the structure, which can there-fore be considered in a similar way to wind.

6.2.3 Flood damageHuge economic and social losses result from flooding in river floodplains and coastalregions subject to storm-surges and vulnerability increases in parallel with economic devel-opment. Floods continue to kill vast numbers of people, particularly in developing countriesthough the toll has declined significantly due to advances in early warning combined withplanned evacuation to safe areas. In the future, climate change may compound the prob-lem through sea-level rise, resulting in degrading of riverbeds and more frequent overtop-ping of banks and levees. It may also enable an increasing percentage of tropical cyclonesto reach coastlines. One study suggests that an increase of about 30% is likely in the num-ber of tropical cyclones which make landfall.

The dangers of floodwaters to the built up environment are associated with a number ofdifferent criteria, not necessarily independent of each other, but creating different types ofclearly recognizable hazards. A summary of the primary criteria and related flood hazardsis given below:

D depth of waterD duration of floodingD flow velocityD rate of rise of river levelD frequency of flood occurrenceD seasonality of inundation

Depth of waterDamage caused by floods is directly related to the depth of the water. Simply, the greaterthe water depth, the greater the amount of damage. Building stability against flotation andfoundation failures, flood proofing, and vegetation survival have different degrees of toler-ance to inundation. In each case these can usually be identified and depth hazard estab-lished.

Duration The degree of damage increases with the duration of the flood. This is largely a result ofthe increasing likelihood of corrosion, and the necessity for post flood cleaning. Durationof inundation is of utmost importance since damage or degree of damage is often relatedto it. This applies to structural safety, the effect of interruption in communications, industri-al activity and public services, and the life of plants.

The duration of flooding can also affect the severity of indirect losses (business interruptionand additional living costs). Clearly, the longer the flooding lasts, the greater the losses.

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VelocityHigh streamflow velocity gives force to flood water, potentially causing:

• erosion of river banks• undermining of riverside objects such as bridges, roads, railways and houses• decreased time for warning and flood preparedness• decreased effectiveness of flood mitigation measures

High velocities of flow create high erosive forces and hydrodynamic pressures. These fea-tures often result in complete or partial failure of structures by creating instability ordestroying foundation support. Dangerously high velocities can occur on the flood plainsas well as in the main river channel.

Rate of riseThe importance of rate of rise of river level and discharge is in its relation to the time avail-able for giving flood warnings or making arrangements for evacuation and flood fightingmeasures. Rate of rise can therefore influence planning permission for flood plain occu-pation, it’s zoning, as well as controlling the mobilisation time of emergency systems.

Frequency of occurrenceTotal potential damage in a flood plain relates to the cumulative effect of depth, durationand velocity hazards measured over a long period of time. This will very often, but notexclusively, influence decisions on planning permission, especially if the hazard can bemeasured in quantitative terms. Cumulative frequency of occurrence of the various haz-ards is therefore a major factor in the development of land use, planning and design ofappropriate prevention and mitigation measures as well as preparedness activities.

Seasonality of inundationInundation of land during a growing season can have a completely destructive effect onagricultural production. Discomfiture and general subsistence levels of affected communi-ties are also considerably influenced if floodwaters occur during cold weather and if theyderive predominantly from snowmelt with possible ice flows. Seasonality in large floods istherefore an important factor controlling the flood hazard.

The other factors influencing the flooding damages and losses, as well related hazards areas given below:

D bedloadD floating debrisD pollutionD post-flooding weather conditions

BedloadBedload can affect the level of damage to buildings and the environment in several ways,though it is rarely of prime importance:

• by causing an increase in the force of flood, and by exacerbating the damagecaused by high flow velocity

• by leading to deposition of sullage in areas where the velocity of the floodwaterhas decreased. Sullage increases loss potential by increasing the need for cost-ly intensive cleaning of both the interior and exterior of the flooded buildings

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DebrisFlooding rivers often carry debris that can lead to blockage of narrower parts of rivers andcross-sections under bridges. This leads to almost immediate overflow of the riverbanks,and can cause severe damage to, or total destruction of, bridges.

PollutionPollution due to waste, fuel, oil, acids, pesticides and other chemicals, as well as morbificagents in the water can dramatically influence the impact of a flood:

• by leading to epidemic outbreaks• by contaminating the land, necessitating enormous expenditure on decontam-

ination• by causing damage to building construction materials

Post-flooding weather conditionsThe weather conditions following a flood may also influence the overall losses. The low tem-peratures or high humidity, for example, can increase the time needed for drying, causingbuildings to be uninhabitable for longer periods, and resulting in increased indirect losses.


D land-use control and locational planning to avoid potential flood plain at the site ofvulnerable elements

D design and construction of structures in floodplain to withstand flood forces anddesign for elevated floor levels

D houses constructed to be flood resistant (water-resistant materials, strong foun-dations); seepage-resistant infrastructure

Substantial progress has been made in preparedness for flooding, issuance of timely earlywarnings and organised evacuations. Around the world, basin-wide land and water man-agement is increasingly being used to mitigate floods and reduce vulnerability to them.Flood-protection structures provide real benefits but can also increase vulnerability byencouraging unwise developments. During floods, the greatest contribution that govern-ments can make is often, however, to enable people to save their lives by warning themand facilitating their evacuation to safe areas. Consequently, provision of timely early warn-ings of flood events is a fundamental contribution to preparedness and mitigation and hasresulted in saving many lives over the past decade.

However, risk assessment remains critically important in mitigating the effects of flooding.There is a need for continuing research and capacity-building efforts to improve prepared-ness and strengthen early warning and other mitigation aspects. Structural measures, landuse and planning approaches, forecasting and warning systems, identification or con-struction of safe havens and public education and awareness initiatives all play vital rolesin achieving these objectives.

6.3 Earthquakes

6.3.1 Mechanism of destructionSeismic energy is transmitted to the earth’s surface from depth in terms of vibration.Vibrations cause damage and collapse of structures, which in turn kill and injure occupants.Vibration may also cause landslides, rockfalls, liquefaction and other ground failures, dam-

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aging settlements in the vicinity, trigger multiple fires, industrial or transportation accidents,and engender floods through failure of dams and other water-retaining embankments.Liquefaction of soils on flat land under strong vibrations in earthquakes is the sudden lossof the strength of soils to support structures allowing them to sink, tilt or fall over (overturn).

6.3.2 Earthquake forcesEarthquakes produce a body force distributed throughout the structure; each particle of itsmass is being multiplied by its corresponding acceleration. This acceleration derives ini-tially from ground movement caused by the earthquake, and can, strictly, be in any of thesix degrees of freedom, that is, three translations and three rotations around the corre-sponding coordinate axes. However, it is usual to consider only the translational degreesof freedom in the horizontal and vertical directions. Such ground accelerations are ampli-fied by the structure itself according to its stiffness and mass distributions, resulting in theforce distribution being quite complex in many instances.

In simple terms, earthquakes produce horizontal forces that can be regarded as beingequal to the mass at each floor level, multiplied by the acceleration at that level. As about90% of the response of multistorey buildings to earthquake occurs in the first, so called‘cantilever-like’ mode, the floor acceleration increases with the absolute height of the floorrelative to the ground. These earthquake forces are transient about a zero mean, with thewhole motion extending over no more than a few tens of seconds at the most.

The local site ground conditions significantly influence the behaviour of buildings and struc-tures. Soil deposits, with their lito-stratigraphic (geometrical stratification and geologicalstructure and composition), physical (material density, modulus of elasticity and shearmodulus, porosity, water content, etc.) and dynamic (period of vibration, damping and vari-ations of physical soil characteristics when exposed to increased alternate dynamic load-ing, etc.) can substantially modify the amplitude and the frequency characteristics ofregional seismic motions.

This amplitude modification, termed usually as amplification of regional motions, is definedas a ratio between the maximum acceleration amplitudes of surface ground motion versuseither the maximum acceleration amplitudes of bedrock motion or the surface motions atdeposits of average soil characteristics. In some cases amplification can reach dramatic lev-els. The typical example is the Mexico City valley. When exposed to action of distant earth-quakes, the accelerations in the valley, composed of lacustrine deposits, are usually 5 to 7times larger than the accelerations generated at the surrounding hills. Transferred into termsof seismic forces, all other conditions being the same, buildings in the valley are exposed to5 to 7 times larger seismic forces than the buildings constructed on outlying hills.

Frequency modification of regional motions counts for filtering characteristics of surfacedeposits. Acting as a filter, the deposit dumps out certain frequencies, and the energy relat-ed to them as well, which are out of its predominant dynamic characteristics. On the otherhand, the energy associated with the frequency range that is close to the deposits’ ownpredominant frequency characteristics is strongly amplified. This energy relocation to aparticular frequency range causes selective damage to buildings. Translated into terms ofseismic forces, only the buildings whose dynamic characteristics are identical or close tothe frequency content transmitted by the deposit will be strongly affected (high seismicforce) and most possibly damaged. Other buildings, whose dynamic characteristic radical-ly differs from the transmitted frequency contents, may not even feel the earthquake (lowor negligible seismic force).

Again the typical example is the Mexico City valley. Damage inventory, following the 1985Michoacan earthquake shows that predominantly 7 to 15 storey building were spectacu-larly collapsed or were heavily damaged, causing substantial human casualty. Others, inparticular low-rise buildings, performed well, and damages recorded were negligible.

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The passage of an earthquake can also have the most serious effects on the bearing capac-ity of the foundation-supporting soil masses, causing either consolidation of loose material,or, where the water table is high, the phenomenon of liquefaction in which the soil loses allits shear resistance. Many of the most spectacular structural failures in earthquakes havebeen rigid-body rotations (overturning) of buildings caused by either foundation failure fol-lowing liquefaction, or resulted from other modes of large ground deformation.

The earthquake response of a building is governed by its dynamic properties, which, inturn, depend on the distribution of mass and stiffness. Of these dynamic properties, thebuilding is period of vibration and its damping are the most important and certainly the mostdifficult to determine accurately. Plan and vertical regularity of structures are also importantand it should not be forgotten that the vertical component of an earthquake motion increas-es and decreases the effect of gravity in a time-dependent fashion.

6.3.3 General factors affecting the seismic vulnerability of buildingsThere are a number of different factors that affect the overall seismic vulnerability and dam-age potential of buildings. Undoubtly, the crucial one is the construction type. It is detailedin subsequent chapters, so no further systematic concern will be presented herein. The dis-cussion presented below is generally applicable to all types of structures, both engineeredand non-engineered as well as structures with or without any level of seismic protection.

Quality and workmanshipIt is common sense to say that a building that is well built, will be stronger than one that isbadly built. The use of good quality materials and good construction techniques will resultin a building much better able to withstand shaking than the use of poor materials and slip-shod workmanship. For masonry buildings, the quality of the mortar is particularly impor-tant, and even rubble masonry can produce a reasonably strong building if the mortar is ofhigh quality. Poor workmanship can include both carelessness and cost-cutting measures,such as a failure to properly tie in the parts of the structure. In cases of poorly-built engi-neered structures, it may be that the constructed structure actually fails to meet the provi-sions of the appropriate seismic building code.

State of preservationA building which has been well maintained will perform in accordance with its expected andconstructed strength. A building which has been allowed to decay may be significantlyweaker, sufficiently to reduce it by at least one vulnerability class (Fig. 13). This may beobserved in cases of abandoned buildings, and also in cases where there is an evidentlack of adequate maintenance. A case particularly to be mentioned is that of buildingsalready weakened or damaged by a previous earthquake – strong foreshock, or mainshock. Such buildings can behave very poorly, so when exposed to main shock (afterstrong foreshock), or to a relatively weak aftershock (after the mainshock) they can devel-op disproportionate amounts of damage (including collapse).

Quite frequently a building may appear to be in good condition because particular atten-tion has been given to maintaining the aesthetic appearance of the building only (freshplastering, nice paint, etc.). However, it does not necessarily mean that the structural sys-tem of the building is also in a good condition, being retrofitted or even strengthened.

RegularityThe ideal earthquake resistant building would be a cube in which all internal variations instiffness (like stairwells) were symmetrically arranged. Since such buildings would beimpaired functionally and depleted aesthetically, the architectural practice encountersgreater or lesser variations from this perfect arrangement. The greater the deviation fromregularity and symmetry (in plane or elevation), the greater is the vulnerability of the build-

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ing to earthquake shaking. In many past earthquakes it is regularly observable how irreg-ularity contributes to the damage. The most drastic cases are demonstrated by so called‘soft-storey’ collapses (vertical stiffness irregularity).

Irregularities in the building plane are easily identified. Buildings with L-shaped groundplane or of similar forms are often subject to torsional effects, which greatly increase thepotential damage. It would be unwise to assume that a building meets standards of regu-larity solely on the grounds of possessing symmetry in its external dimensions. Even if theground plan is regular, problems may arise in buildings with marked asymmetry in the geo-metrical arrangement of internal components or in the arrangement of components withradically different stiffness characteristics. The position of elevator shafts and stairwells isoften noteworthy in this respect.

Buildings in which one storey (usually the lowest) is structurally significantly more flexibleand weaker than the others are regarded as ‘soft-storey’ buildings. This, extremely frequentvertical irregularity, is because the first building stories are often used as stores and com-mercial spaces, especially in the central parts of cities. These areas are usually enclosedwith glass windows, and sometimes with a single masonry infill at the back. Continuousstrips of window over the length of the building in its elevation may also introduce similareffects, weakening that particular storey.

Soft storey buildings are highly prone to collapse. During an earthquake, the presence ofa soft storey increases deformation demands very significantly, and puts the entire burdenof energy dissipation on the soft storey, as opposed to the concept of distributing the bur-den along the entire height of the building. Many failures and collapses in past earthquakescan be attributed to the increased deformation demands caused by the soft stories, in par-ticular when coupled with the lack of deformability of poorly designed columns.

The most unfavourable behaviour is associated with soft-storey buildings with an openstreet facade and solid back-walls. They tend to collapse toward the street as a result ofthe torsional plan eccentricity. In such cases, the soft-storey sway is greater on the moreflexible side of the facade, resulting in greater displacement and ductility demands on themore vulnerable columns on the facade side.

Collapse mechanisms of small masonry buildings

Mechanisms causing partial collapse1) Developing of diagonal cracking and the displacement of the wall corner; 2) Developing ofdiagonal cracking and the displacement of the end wall; 3) Developing of vertical cracks; 4)Dropping of poorly supported wall above windows and doors; 5) Falling chimney; 6) Collapse of aportion of the roof; 7) Collapse of a weak area often associated with the position of a floor joist; 8)Collapse of a central section of wall for example around windows and above large cracks.

(Source: Hughes, 1981)

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Mechanisms causing total collapseWhen shaking starts the loose structural members in a building are first to fall. If walls are notsecurely bounded to each other they may simply burst (A); or if floor and roof joists are not well tiedinto them, the beams may come out and wedge the walls apart (B) or batter them down (C).

A. Wallbursting:

1) External wall bursts into multiple units, mostly outward, occasionally inward; 2) Collapse as a sin-gle unit, mostly inward, occasionally outward; 3) Downward collapse of roof; 4) Collapse of floorjoists usually from one end; 5) Foundation failure

B. Floor-joist collapse:

1) Joists come out and floor collapse [usually at one end]; 2) Wall falls as two units, down and out-wards; 3) Wall splits and mostly falls/slumps outwards; 4) Downward collapse of roof; 5) Top of wallpushed outward by failing roof; 6) Top of wall pushed outward by failing joist; 7) Decayed materialfalls out at base of wall

C. Roof collapse:

1) Roof collapses downward onto floor; 2) Displaced block of masonry falls vertically and disinte-grates (3) into a pile of rubble; 4) Joists come out and floor collapse [usually at one end]; 5)Collapsing floor joist by a pivoting action forces off a portion of wall above the joist-wall socket; 6)Outward collapse as multiple small units but leaving a stub of in citu wall above.

Collapse mechanisms of small masonry buildings

(Source: Hughes, 1981)

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A Two wings at right angles with different motions causing damage at the connection points

B Building of varying height producing different resonance frequencies

C As the waves move up the building, the shaking is amplified at the top

D Pounding between adjacent buildings because of different phases of the motion

E Enhanced swaying because of alignment of structures relative to the direction of incoming wavemotion

F Flexible high rise buildings with different architecture: Design (a) remains elastic, while "soft"ground floor in (b) has no shear resistance

G Pair of buildings on different soils: (a) on rock which transmits higher frequency waves; (b) onsofter soil layers which set up wave resonance requiring special bracing of the structure.

Effect of strong ground shaking on high-rise buildings

A B

C D

E

F

Ga

b

a

b

(Source: Bolt, 1988)

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In many cases soft-storey collapses are the main cause of partial or total blockage ofstreets and inaccessibility for efficient post-event emergency operations.

In some cases, buildings that previously had a good level of designed and constructed reg-ularity may later be adversely affected by subsequent modifications. For example, conver-sion of the ground floor of a building into a garage or shop may weaken it (creation of asoft storey); or construction of building as an extension to an existing building is likely tomake the ground plan more irregular. Old masonry buildings may have been extensivelymodified over a long history, resulting in offsets of floors at different levels, foundations atdifferent slope levels, and so on.

DuctilityDuctility is a measure of a building’s ability to withstand lateral loading in a post elasticrange, that is, by dissipating earthquake energy and creating damage in a controlled widespread or locally concentrated manner. The ductility depends on the type of constructionmaterial and the structural system. Ductility can be a direct function of construction type:well-built steel houses have high ductility, and therefore resist shaking well, compared tomore brittle lower-ductility buildings such as, for example a brick masonry buildings. Inseismically resistant buildings, the parameters controlling the building dynamic perform-ance (stiffness and mass distribution) shall be ensured including the qualitative energytransformation and dissipation. Otherwise, the energy will concentrate in brittle (non duc-tile) elements, leading to critical local damage concentrations.

PositionThe position of a building relative to other buildings can affect its behaviour in an earth-quake. In the case of a building-row in an urban block, it is often those buildings at the endof a row or in a corner position that are the worst affected. This is because one side of thebuilding is usually anchored to a neighbouring one, while the other is free. It causes anirregularity in the overall building stiffness that usually leads to increased damage levels.

Severe damage of buildings within the urban block can be the result of the so-called ‘pond-ing’ effect. The ponding effect develops between the buildings of radically different stiffnesscharacteristics (for example taller and more flexible and lower and stiffer), which are placedtoo close to each other (non-existence, or non adequate seismic joint). Because of differ-ent deformation patterns during the process of shaking, the stiffer building is blocking thesway of the taller and more flexible building, causing damage to both. The damage may beconcentrated at the pounding heights only; however, the heavy damage at the pondingspot may progress to partial or even total collapse of one or both buildings. If buildings ofthe same height are placed too close to each other, they can smash into each other, devel-oping similar damage patterns with the same potential consequences as alreadydescribed.

6.3.4 Factors affecting the seismic vulnerability of RC buildingsRC is made from materials which are available almost everywhere, and its basic proper-ties are reasonably well understood by engineers and builders. Its high durability, fireresistance, and other properties that allow the construction of large and multistorey struc-tures with relative ease have made it the most common material worldwide for buildings ofmore than three stories. As a result, in rapidly expanding urban areas of the developingworld, the number of RC buildings is increasing. Many of these areas are in zones of seis-mic activity and most of the RC buildings there are expected to experience earthquakeshaking at least once in their lifetime.

The experience of recent earthquakes has given cause for concern about safety standardsin RC construction in many parts of the world. In earthquakes in Caracas (1967), San

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Fernando, California (1971), Managua (1972), Bucharest (1977), Italy (1976, 1980),Greece (1978, 1981, 1986, 1999), Mexico City (1985), El Salvador (1986), Armenia (1988),Philippines (1990), eastern Turkey and Egypt (1992), Kobe (1995), Turkey (1999), Taiwan(1999) many RC buildings collapsed because they were not designed and/or constructedto resist the shaking which they experienced.

In developed countries such failures have served as lessons to the engineering communi-ty, the necessary conclusions have been drawn, and reflected in the updating of seismiccode provisions; this has contributed to a drastic reduction of earthquake losses. However,the dissemination process has been quite slow in developing countries, where RC build-ings became commonplace much later.

A code of practice appropriate to the place where the building is to be built must be fol-lowed. Codes of practice are complex documents containing many detailed requirementsand recommendations. They need interpretation by experienced engineers. Stringentchecks by the local authorities at both the design and construction phase are also neededto ensure their proper application. The desired progress has not yet been achieved andtherefore disasters will continue to happen as long as safety standards are not upgraded.

The most common reasons involving RC failures in earthquakes are:

D poor understanding of the way RC behaves during earthquakesD insufficient knowledge in the geotechnical field that allows inadequate practices in

areas of high riskD Low perception of risk by engineers, developers and owners associated with poor

practices knowingly or unknowinglyD Insufficient institutional development for code enforcement at the design and con-

struction phaseD Precedence of cost or other considerations over those of structural safety; etc.

In addition to the general factors already presented affecting the seismic vulnerability ofbuildings, the following are additional and specific to RC structures, only.

Vertical irregularityThis poor design factor, or factor created by owners due to improper interventions in build-ing, may lead to excessive building damage. Quite frequently, in order to decrease the costof the structural system, at a certain height of the building, the designers decrease thedimensions of columns, or even replace the shear walls with columns. The owners, in orderto upgrade the building without strengthening the lower part, erect upgrading structuresusing lighter steel elements. This leads to excessive axial force in the place of abrupt stiff-ness changes, and, most frequently, to the partial collapse of the upper part of the building

Shear failure of RC panelsFrequent openings in shear panels (doors and windows) reduce the effective shear areaof the panel. Failure to account for this by commensurate design of other structural meas-ures leads to cracking of the panel.

Short-column effectThe ‘short column’ effect is a result of changes in stiffness of structural elements due toadjoining rigid non-structural elements. The effect is typical for external building columns.The external sill walls shorten the external columns leading to increased stiffness andhence high loads in a short section of the column. During an earthquake this lead to shearcracking in the columns. This effect, known as the ‘short-column’ effect, may be regardedas a result of poor ductility detailing.

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Strong beams and week columnsIn most frame structures, beams are designed and constructed to be stronger than sup-porting columns. Consequently, strong beams remain elastic, and the weaker columns suf-fer damage and failure in the form of compression crushing, plastic hinging, or shear fail-ure. In many cases engineers without experience in earthquake engineering are designingrelatively deep beams with flexible columns, contributing unintentionally to strong-beamweak-column behaviour of the building. Whenever damage develops in columns withoutductile details, strength and stiffness degradation will be further precipitated by the pres-ence of axial forces. Excessive damage not only means loss of buildings’ lateral loadresistance, but also, as demonstrated by many past earthquakes, loss of gravity loadsresistance and collapse.

Lack of column confinement and poor detailing practiceMost structural damages inventoried in past earthquakes for RC frame buildings demon-strate that damage concentrates at column ends. Unfortunately, the confinement rein-forcement (stirrups) was virtually nonexistent, or placed at such distances, that columnswere unable to maintain the required ductility.

Several of other detailing deficiencies are quite typical for improper detailing of RC build-ings: lack of anchorage of beams and columns for reinforcement, insufficient splicelengths, use of 90° hooks, poor concrete quality, less than full height of masonry infill par-titions, and frequent combinations of many of the above. These errors are often com-pounded by geometric irregularities such as eccentric beam-to-column connections thatinduce severe torsion.

Cracking of non-structural walls adjoining or between structural elementsIf appropriate measures are not undertaken, the stiffer non-structural walls restrain thedeformation of more flexible frames. This results in shear-slip and/or cracking of the non-structural masonry walls. However, if the stiffness of the infill panels is very high, they canseriously damage the columns of the RC frame itself.

Poor quality of constructionPost earthquake studies provide much evidence of honeycombed or segregated concretewith round (that is, unsatisfactory) aggregate. The measured strength of many concretesamples taken after the earthquakes have shown that the concrete strength was wellbelow the local standards and code requirements. In addition, use of straight reinforcingbars instead of deformed, reduces the required ductility of concrete frames.

6.3.5 Effects of earthquake shaking on tool buildingsThe oscillatory forces produced by earthquakes cause a series of characteristic failure pat-terns in buildings. Tensions results in the thinning or open cracking of structural members,which is a particular problem in materials that lack ductility, such as concrete. Compressioncauses crushing of wide (thick) members and slender one to buckle. Buckling is the more dan-gerous of these two processes, as it tends to occur suddenly. As columns deform, beams suf-fer compression on the concave and tension on convex side. Walls can shear through andoverturn, while the connection between columns and floor slabs can result in a "punch-through" and collapse of the horizontal member. Vertical members suffer concentration ofshear forces at their tops and bases, which may cause them to hinge in these zones.

The inertial sway occurring during the earthquake concentrates the force of the shaking atground level in the form of highly destructive basal shear and/or overturinig moment, whichoften, alone or combined, can cause settling and compression of lower floors before therest of the building has weakened to the point of collapse. Other forms of inertia may also

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be present, depending on the distribution of weight and strength in the building. For exam-ple, vertical compression may interact with the inertia at the top of the building to crash themiddle floors, or the greater amount of sway (and hence distortion) may cause the topfloors to collapse first.

Buildings with L-shaped ground plane or of similar forms are often subject to torsionaleffects, which greatly increase the potential damage. Even if the ground plan is regular,problems may arise in buildings with geometrical asymmetry in vertical plane, markedasymmetry in the geometrical arrangement of internal components or in the arrangementof components with radically different stiffness characteristics.

'Soft-storey' buildings are buildings in which one storey, usually the lowest, is structurallysignificantly more flexible and weaker than the others. Continuous strips of window overthe length of the building in its elevation may also introduce similar effects, weakening thatparticular storey. Soft storey buildings are highly prone to collapse.

The ponding (hammering) effect develops between the buildings of radically different stiff-ness characteristics (for example taller and more flexible and lower and stiffer), which areplaced too close to each other. The damage is severe and may be concentrated at thepounding heights only. However, the heavy damage at the ponding spot may progress topartial or even total collapse of one or both buildings. If buildings of the same height areplaced too close to each other, they can smash into each other, developing similar dam-age patterns with the same potential consequences.

6.3.6 Earthquake damageEarthquakes are amongst the most damaging natural phenomena to affect the earth. Over1.6 million people have died in earthquakes during the 20th century while huge economiclosses have been incurred. The moderate (Richter scale 7.2) 1995 earthquake in Kobe,Japan, for example, produced direct economic losses reaching a new record of over $140billion. Earthquake damage is, in general, related to the magnitude of the event, the qual-ity of buildings and structures and the nature of the ground. Secondary effects such asfires, landslides and tsunamis frequently contribute substantially. In 1960, a magnitude 5.9earthquake caused approximately 12,500 deaths in Agadir, Morocco, where traditionalstone and brick houses were situated on loosely consolidated sediments. In contrast, amagnitude 6 earthquake in the Canadian Shield in 1988 caused no deaths in a regionwhere houses are usually wood framed with relatively light roofs. However, earthquake vul-nerability is increasing rapidly worldwide, as a result of flaws in planning, siting, design,construction and use of buildings, dams, transportation links and other infrastructure ele-ments.


D design and construction of structures to withstand vibration forces; seismic build-ing codes

D enforcement of compliance with building code requirements and encouragementof higher standards of construction quality

D construction of important public sector buildings to high standards of engineeringdesign

D retrofit, strengthening of important existing buildings known to be vulnerableD locational planning to reduce urban densities on geological areas known to ampli-

fy ground vibrationsD insurance

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Earthquakes will, inevitably, continue to occur, particularly along the boundaries of tecton-ic plates, but it cannot be predicted exactly where, when or what will be their magnitude.In a few regions, however, useful early warning systems are possible for approaching seis-mic waves from distant earthquakes and such systems have been implemented in a fewlocations. Their effectiveness is dependent on a very fast seismographic and computer-communications infrastructure capable of disseminating information in advance (that is,within seconds to a minute or so) of the arrival of dangerous shear and surface waves.

However, every penny spent on mitigation and preparedness is estimated to save ten pen-nies in recovery and reconstruction costs, emphasising that earthquake mitigation and pre-paredness makes economic sense. The basic scientific and technical information requiredto characterise earthquake hazard and community vulnerability is now readily available inall countries. The general level of seismicity across broad areas can be forecast for thenext tens to hundreds of years and nearly all countries now have regional seismic hazardmaps. The next step towards preparedness is to conduct detailed vulnerability studies.

Reduction of vulnerability to earthquakes is, clearly, an urgent goal for the comingdecades. It is, moreover, one that is possible to realise as policy makers now have manyearthquake mitigation options available. These include insurance, construction codes andstandards, remediation and retrofit, demolition of hazardous structures, relocations, sitingand land-use criteria, training and exercises. The key to success will be to integrate riskassessment and risk management as an ongoing strategy aimed at avoidance of flaws inplanning, design, siting, construction and use which create or increase vulnerability.

6.4 Snow avalanches

6.4.1 Mechanism of destruction:An avalanche is a mass of snow sliding down a mountainside. Avalanches destroy struc-tures, roads and cables, and cut communication lines either by the snow moving downfrom the higher altitudes, or by burying them. They fill valleys, burring individual buildingsand even settlements, blocking rivers and roads, affecting the bridge structures and othersurface transport facilities. Avalanches are a major hazard in many mountainous countries.They result in substantial loss of life, such as the 75 fatalities recorded in the EuropeanAlps during January-February 1999, with numerous others injured, as avalanches struckski resorts and mountain villages.

6.4.2 Types and structure of avalanchesThere are three different types of avalanches:

• wet-snow avalanches• slab-snow avalanches• powder snow avalanches

Powder snow avalanches are the most dangerous. They don’t make much sound, areunpredictable and could reach speeds of up to 200 kilometres per hour. Wet-snow ava-lanches make a loud noise and happen when the temperature rises. The snow slips down.Slab-snow avalanches happen when a new layer of snow falls on an old layer. The newlayer does not integrate with the old layer and the new layer can slip off the old layer.

Avalanches are made up of two parts, the upper-part and the under-part. During the ava-lanche, the upper-part has more speed than the under-part, so the upper-part rolls over theunder-part and becomes an under-part itself, losing speed because of trees and otherobstacles. The old under part in turn rolls over the old upper-part and becomes itself anupper-part.

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6.4.3 Period of danger and locations of occurrenceAvalanche danger increases with major snowstorms and periods of thaw. About 80% of allavalanches fall during or just after large snowstorms. According to European data (Alps),the most avalanche-prone months are, in order, January, February, April and March.Avalanches caused by thaw occur most often in April.

About 90% of all avalanches start on slopes of 30° to 45°; about 98% of all avalanchesoccur on slopes of 25° to 50°. Avalanches are released most often on slopes above thetimberline that face away from prevailing winds (leeward slopes collect snow blowing fromthe windward sides of ridges.) Avalanches can run, however, on small slopes well belowthe timberline, such as gullies, road cuts, and small openings in the trees. Very dense treescan anchor the snow to steep slopes and prevent avalanches from starting; however, ava-lanches can release and travel through a moderately dense forest. Most avalanches occurin the backcountry, outside developed ski areas.

6.4.4 Recognition of avalanche terrains and unstable snowMost large avalanche paths are obvious: an open slope, bowl, or gully above the timber-line that leads to a swath through the trees. But small avalanche paths in the trees can bejust as dangerous. The slope angle is the most important and critical factor. Snow deposi-tion patterns and the effects of anchors such as rocks or trees that might prevent ava-lanches on some slopes shall be observed. Bent or damaged trees are good clues thatshow where avalanches have run in the past.

When the snow cover is very unstable, nature often broadcasts clear danger signals. Freshavalanches are the best clue. Snow that cracks, collapses, or makes hollow sounds is alsounstable. Weak layers that are found by digging snow pits are signs of unstable snow.Snow that has become wet from thaw or rain can also be dangerous.

6.4.5 Avalanche forcesSnow avalanche movements translate into high external loading on structures (Table 16).Using reasonable estimates for speed and density, it is estimated that maximum directimpact pressures should be in the range of 5-50 tonnes /square metre (t/m2), although somepressures have been known to exceed 100 t/m2. A guide to the relationships between ava-lanche impact pressures and the likely damage to man-made structures is presented inTable 16. In addition to the direct impact, avalanches may exert upward and downwardforces, which have been known to lift large locomotives, road graders and buildings.

Impact pressure (t/m2) Potential damage

Table 16 Relationship between impact pressure andthe potential damage from snow avalanches

/Perla and Martinelli, 1976/

0.1

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Breaks windows

Pushes in doors

Destroys wood-frame houses

Uproots mature trees

Moves reinforced concrete structures

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6.4.6 Avalanche damageAvalanche damage can also be very substantial (reaching 1 billion Swiss francs inSwitzerland during the past winter, for example). Around the world, vulnerability to ava-lanches will continue to increase as winter recreational activities and facilities expand inmountainous regions.


D Long-term measures• avalanche hazard mapping and risk assessment• land-use planning• development of protective forests and installation of protective structures

D Short-term measures• avalanche forecasting• the issue of avalanche warnings• artificial releases of snow masses• road and rail closures, and evacuations

Some governments already invest heavily in such avalanche protection measures becauseof their demonstrated cost effectiveness. Over the past 50 years, for example, about 1.5billion Swiss francs has been invested in protective structures in Switzerland, in addition tothe resources devoted to forecasting, hazard zoning and protective forests.

Implementation of avalanche risk assessment and risk management is fundamental to theachievement of reduction in vulnerability. While this approach is already in place in somecountries, it needs to be extended to other vulnerable regions. In order to improve its appli-cation, there is a need for continued research into snow pack physical processes,improved avalanche forecast and hazard mapping techniques, better technical and con-struction measures and enhanced risk management methods.

6.4.8 Tips for avalanche survival

Avoiding an avalancheAvalanches can reliably be avoided by recognising and avoiding avalanche terrain.Travellers should use the valley floors away from large avalanche run-outs, along ridge-tops above avalanche paths, in dense timber, or on slopes of 25° or less that do not havesteeper slopes above them. Cornices on ridge-tops should be avoided.

Risky travel in avalanche terrain cannot be entirely eliminated, but it can be minimised byusing good techniques, such as: climbing, descending, or crossing avalanche areas oneat a time; crossing a slope at the very top or bottom if possible; climbing or descending theedge of a slope rather than the centre; carrying and knowing how to use avalanche rescuegear; and turning back or altering the route if the signs of unstable snow are detected.

Precaution measuresBefore crossing a slope where there is any possibility of an avalanche, fasten all your cloth-ing securely to keep out snow. Loosen your pack so that you can slip out of it with easeand remove your ski pole straps. For those wearing avalanche beacons, make sure thatyour avalanche beacon is on and switched to “transmit” rather than “receive.” Cross theslope one at a time to minimise danger.

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What to do if caught in an avalancheSurviving avalanches can depend on luck; therefore, it is always better to avoid them in thefirst place. Statistics show that only 1 in 3 victims buried without avalanche rescue gearsurvives.

If you are caught, first try to escape to the side, or grab a tree or rock. Yell and let go ofyour ski poles and get out of your pack to make yourself lighter. Use “swimming” motions,thrusting upward to try to stay near the surface of the snow. Try to avoid trees. When theavalanche slows down, try to reach the surface or make an airpocket. When avalanchescome to a stop and debris begins to pile up, the snow can set as hard as concrete. Unlessyou are on the surface and your hands are free, it is almost impossible to dig yourself out.If you are fortunate enough to end up near the surface (or at least know which direction itis), try to stick out an arm or a leg so that rescuers can find you quickly.

If you are in over your head (not near the surface), try to maintain an air pocket in front ofyour face using your hands and arms, punching into the snow. When an avalanche finallystops, you will have from one to three seconds before the snow sets. Many avalanchedeaths are caused by suffocation, so creating an air space is one of the most critical thingsyou can do. Also, take a deep breathe to expand your chest and hold it; otherwise, you maynot be able to breathe after the snow sets. To preserve air space, yell or make a noise onlywhen rescuers are near you. Snow is such a good insulator they probably will not hear youuntil they are practically on top of you.

Above all, do not panic. Keeping your breathing steady will help preserve your air spaceand extend your survival chances. If you remain calm, your body will be better able to con-serve energy.

In summary, here are some points when you see an avalanche coming to you:

D get away from the centreD take off your ski and baggageD if possible, jump as high as you canD put your hand before your eyes to have more airD use ‘swimming’ motions to try to move up and stay near the surface of the snowD take a deep breath to expand your chest and hold itD try to reach the surface when the avalanche slows down or make an airpocketD if you end up near the surface (or at least know which direction it is), try to stick

out an arm or a leg so that rescuers can find you quicklyD do not panic. Keeping your breathing steady will help preserve your air space and

extend your survival chances

6.4.9 Rescuing a victimTry to watch the victim as they are carried down the slope, paying particular attention tothe point where you last saw them. After the avalanche appears to have finished and set-tled, wait a minute or two and observe the slope carefully to make sure there is no furtheravalanche danger. If some danger does still exist, post one member of your party in a safelocation away from the avalanche path to alert you if another avalanche falls.

When travelling with a large party, you may want to send someone for help immediatelywhile the rest of you search. If you are the only survivor, do a quick visual search. If youdo not see any visual clues, and you do not have transceivers, then go for help.

Begin looking for clues on the surface (a hand or foot, piece of clothing, ski pole, etc.),beginning with the point where they were last seen. As you move down the slope, kick over

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any large chunks of snow that may reveal clues. Since equipment and items of clothingmay be pulled away from a victim during an avalanche, they may not indicate their exactlocation, but can help determine the direction the avalanche carried them. Mark thesespots as you come across them. Be sure that all rescuers leave their packs, extra clothing,etc., away from the search area so as not to clutter or confuse search efforts.

Once the victim is found, it is critical to pull them out as quickly as possible. Survivalchances decrease rapidly depending on how long a victim remains buried. Treat them forany injuries, shock, or hypothermia if necessary.

If you lost sight of the victim early during the avalanche, or if there are no visible clues onthe surface, mark where the victim was last seen. Look at the path of the snow and try toimagine where they might have ended up. For those wearing avalanche transceivers,switch them to “receive” and try to locate a signal.

For those using probes, begin at the point where the victim was last seen. Or, if you have agood idea of where they were buried, begin in that area. Stand in a straight line across theslope, standing shoulder to shoulder. Repeatedly insert the probes as you move down theslope in a line. Pay particular attention to shallow depressions in the slope and the uphillsides of rocks and trees, since these are terrain traps where they may have been buried.

It may be necessary to probe certain areas more than once if you don’t locate the victimthe first time around, but this takes more time and decreases the victim’s chances for sur-vival. Similar to using transceivers, this method of rescue is much more effective if thoseinvolved have experience or have practiced finding buried victims using probes.

After searching for clues, or using transceivers and/or probes, still does not reveal the loca-tion of the victim, it may be time to rely on outside help. Nearby ski resorts will be staffedwith personnel experienced to handle these situations. They will have equipment to locatethe victims and dig them out (if your party did not bring shovels or probes), and they mayalso have avalanche dogs that can help find victims. Ski area patrollers will also have firstaid equipment, but unfortunately, by the time they can usually reach out-of-bounds ava-lanche accidents, too much time has elapsed to save the victim.

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7. Building typology and classificationDuring the past two decades natural disasters, and earthquakes in particular, have tendedto become increasingly destructive as they affect an ever-larger concentration of popula-tion and material property. Industrial development of seismic-prone regions, which is ordi-narily accompanied by urban expansion and increased population growth becomes pro-hibitive, unless investments in infrastructure, housing, other public and social activities, etc.are protected against damage at all stages of their development.

In order to forecast damages which are expected to occur during future earthquakes, it isnecessary to understand how various types of structures will behave when exposed toground shaking of different intensities. The same knowledge is also essential for cost-ben-efit studies to determine the relative effectiveness (decrease in specific loss) of various pos-sible measures for seismic risk mitigation, such as estimating the genesis of earthquake-induced damages, possible collapse mechanisms including the possible death and injurypotential, and defining adequate resources and organisation of emergency response.

Although at any intensity of ground shaking all buildings of similar types and size will notrespond equally, damage must be documented for enough similar structural types for thesame shaking intensity, so that both an average damage level and the dispersion estimatorsof damage can be determined and allocated to the class of buildings under consideration.

While a variety of subclasses may be defined within each of the generally defined buildingclasses (for example, in respect to the type of floor or roof structure used, the type of exte-rior or partition walls and construction materials used, etc.) for damage and casualtyassessments and related needs, five broad classes of buildings and houses may general-ly be considered to reliably represent the variety of structural types used traditionally forurbanization in the Balkan Peninsula, Mediterranean and Europe.

The general building classification scheme, used principally for large-scale damage andcasualty assessment modelling and seismic risk analysis is presented in Table 17 andFigs. 9 to 12.

The illustrations (Figs. 9 to 12) are simplified pictorial descriptions of the large majority ofbuildings in each building category. They have been included with the intention to supportdescriptions given in Table 17, as well as to enable those who are unfamiliar with designand construction practice to recognize the classes of structures covered by the classifica-tion scheme.

In this material consistent treatment is given to adobe & earth brick and timber construc-tion as well as steel structures. The reason is that adobe & earth brick structures arenowadays usually altered by modern building typology, so their number is rapidlydecreased in urban regions. This is particularly true in the urban regions that for last sev-eral decades have a record of accelerated development. As for the timber construction, itis not often encountered in seismically prone regions of Europe, or they are located inmountain or resort locations posing no systematic or mass threat to its occupants.

However, for the completeness of the material, some discussion on their construction char-acteristics and seismic resistance is presented below.

Adobe & earth brick: This type of construction can be found in many places where suit-able clays can be found. Methods of adobe construction vary widely, and this introducessome variations in the strength of adobe houses against earthquake shaking. Walls builtup of layers of adobe without the use of bricks are stiff and weak; brick houses may per-form better depending on the quality of mortar, and, to a lesser extent, on the quality of thebrick. The weight of the roof is one of the most important factors in the performance of suchhouses, heavy roofs being a liability. Adobe houses with wooden frames possess added

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strength and perform significantly better. Such buildings may suffer damage to walls rela-tively easily, while the wooden frame remains intact due to its higher ductility. One alsoencounters cases where unconnected wooden beams and columns are used in adobehouses; these provide extra horizontal stiffness and therefore improved performance, butnot so much as a connected frame would do. The type of housing encountered in someparts of Europe known as “wattle and daub”, where a wooden frame is filled in with lathscovered with clay, is similar to adobe/wood construction.

The number of adobe & earth brick constructions in urban areas is negligible, and thus theydo not pose any serious hazard to its occupants and contents. A larger number of theseconstructions still exist in rural or semi rural areas in certain parts of Europe.

Wooden structures: The innate flexibility of wooden constructions gives them a highresistance to damage, though this can vary considerably as a function of conditions. Loosejoints or rotten wood can make a wooden house quite vulnerable to collapse. This wasquite notable in the case of the Kobe earthquake of 1995 that traditional wooden housesin parts of the city performed very badly because of their poorly preserved condition. Thisis a very good example of how vulnerability depends on something quite other than build-ing construction type.

The structural system providing lateral resistance should be considered carefully. If thebeam and columns are connected by nailed plates (of gypsum and other brittle materials),or if these connections are weak, the structure will fail if connections fail. This type of tim-ber structure should be distinguished from timber frame structures which are resistantagainst lateral loads caused by earthquake shaking. The ductility of wooden structuresdepends on the ductility of the connections.

Steel Structures: Steel structures are buildings for which the main structural system is pro-vided by steel frames. While their technology of construction differs radically from the con-struction of reinforced concrete (RC) buildings, in many other structural aspects they aresimilar to these (transport of gravity loads, stiffness of floor structures relative to the stiffnessof columns, infill panels, etc.). The basis difference is the material used to construct the prin-ciple structural system (steel instead of RC). The existing macroseismic evaluations indicatetheir high level of earthquake resistance. Structural damage may, however, be masked bynon-structural elements such as cladding or curtain walls, or concrete additions (provided toincrease fire resistance) in composite systems. In such cases, damage to the joints of theframe will be visible only after the concrete cover has been removed.

The decision made on the level of earthquake resistance should in particular be reflected inthe stiffening system as well as the type of joint connections. The ductility of the entire systemis determined by the lateral load resisting system (that is, the frame type and kind of bracing).

The vulnerability of steel frame buildings without special aseismic measures or non-seis-mically resistant designed steel buildings is similar to the vulnerability of RC buildings witha moderate level of seismic protection. Bracing that affects columns (K-bracing) providesless earthquake resistance. In most cases moment-resisting frames, frames with RC shearwalls/core, or frames with eccentric or X- or V-bracing provide increased resistance to lat-eral loading and ensure ductile behaviour.

The relative vulnerability of different classes of structures (buildings) is presented in Fig.13. Structures of the highest vulnerability (field stone, rubble stone and adobe & earth brickmasonry) are typical, examples of Class A vulnerability. Earthquake-resistant designedshear wall buildings or steel moment-resisting frames, steel frames with RC shearwalls/core are typical examples of low vulnerability class, that is, the Class E. Class F rep-resents buildings of lowest vulnerability (moment-resisting steel frames or steel frameswith X- or V-bracings with improved earthquake-resistant design).

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Table 17 General building classification scheme

I CLASS SM-STONE MASONRY BUILDING

Houses and buildings, not over three stories high, constructed of unreinforced solid unit stone mason-ry where loads are completely or partially carried by walls and partitions.

Interior partitions are generally of stone masonry, rarely of brick and other masonry (adobe, hollow unitmasonry etc.). The load-carrying stone masonry walls may be constructed as dry stone masonry, plainor simple stone with low quality of mortar, plain stone with good quality of mortar, stone masonry withtimber belts, stone masonry with steel ties, stone masonry with RC horizontal or with RC horizontal andvertical belts, etc. Stone masonry systems with RC and steel elements are recently in use and may beconsidered as systems strengthened to withstand seismic loading.

Roofs and floors may be of any material. Traditional wooden floors are nowadays replaced by rein-forced concrete slabs on reinforced concrete beams. For roofing any type of reinforced concrete floors,tiled wooden structure may be used as well.

Houses and buildings, not over three stories high, having unreinforced solid unit masonry of unrein-forced brick or unreinforced concrete solid or hollow unit brick, where the loads are completely or par-tially carried by walls and partitions. Interior partitions may be of any of the aforementioned materials.

Roofs and floors may be of any material. Traditional wooden floors are replaced by reinforced concreteslabs or reinforced concrete slabs on reinforced concrete beams. A tiled wooden structure or any typeof reinforced concrete floors is used for roofing.

Houses and buildings, not over three stories high, having superior earthquake damage control featuresincluding exterior walls of (a) reinforced solid brick masonry and/or (b) reinforced hollow brick mason-ry or reinforced concrete brick masonry and/or (c) reinforced hollow concrete block masonry.Strengthening of exterior and/or interior bearing walls is performed by horizontal RC belts at story lev-els or by horizontal and vertical RC belts connected also at story levels. Interior partitions or bearingwalls may be of any aforementioned material.

Roofs and floors may be of any material. Reinforced concrete slabs, reinforced concrete slabs on rein-forced concrete beams and/or cast-in-place reinforced concrete slabs on hollow brick units supportedby reinforced concrete beams. Any of the aforementioned floor structures or a tiled wooden structuremay also be used for roofing.

Buildings having a complete poured-in-place reinforced concrete frame with all loads carried by thereinforced concrete frame. Exterior, interior and partition walls may be of solid brick masonry, hollowbrick and concrete masonry, light concrete blocks, prefabricated light panels or of any non-load carry-ing material. Floors and roof should be of RC slabs, RC slabs on RC beams in one or both directions,reinforced concrete lift slab floors, etc. This class of buildings does not include buildings having col-umn-free areas greater than 50 square metres (such as auditoriums, theatres, public halls, etc.).

Buildings having superior earthquake damage control features. Structural system consists of poured-in-place framed reinforced concrete-bearing walls or connected directly (wall-to-wall connection).Exterior, interior and partition walls may be of solid brick masonry, hollow brick and concrete masonry,light concrete stones, prefabricated light panels or of any non-load carrying material. Floors and roofshould be of RC slabs, RC slabs on RC beams in one or both directions, reinforced concrete lift slabfloors, etc. This class of buildings does not include buildings having column-free areas greater than 50square metres (such as auditoriums, theatres, public halls, etc.).

II CLASS BM-BRICK MASONRY BUILDINGS

III CLASS STM-STRENGTHENED MASONRY BUILDINGS

IV CLASS RCFS-REINFORCED CONCRETE FRAME STRUCTURES

V CLASS RCSWS-REINFORCED CONCRETE STRUCTURES WITH SHEAR WALLS

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Fig. 9 Generalized illustration of a portion of SM structural class

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Fig. 10 Generalized illustration of a portion of BM structural class

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Fig. 11 Generalized illustration of a portion of STM structural class

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Fig. 12 Generalized illustration of a portion of RCF structural class

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Type of structureVulnerability class

A B C D E F

Fig. 13 Differentiation of structures (buildings) in the vulnerability classes/Source: European Macroseismic Scale EMS-98/

Adobe & earth brick

Rubble stone, field stone

Simple (plain) stone

Massive stone

Unreinforced, with manufactured stone units

Unreinforced, with RC floors

Reinforced or confined

Frame without eq. resistantdesign

Frame with moderate levelof eq. resistant design

Frame with high level of eq.resistant design

Walls without eq. resistantdesign

Walls with moderate level ofeq. resistant design

Walls with high level of eq.resistant design

STEEL structures

TIMBER (WOOD) structures

MAS

ONRY

REIN

FORC

ED C

ONCR

ET

Most likely vulnerability class

Probable range

Less probable range, exceptional cases

Class A represents construction of highest vulnerability; Class F of the lowest

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8. Post-earthquake damage and usability inventory and classificationThe post-earthquake damage and usability inventory of structures is performed by apply-ing the criteria for damage and usability classification of building structures detailed inTable 18. The major concern of damage classification criteria is the damage state of theprincipal load-carrying system since it is of primary importance for post-earthquake stabil-ity of damaged buildings and the safety of the occupants.

During the process of post-earthquake damage inspection it is essential to carry out in par-allel the following two interrelated classifications:

D physical damage assessment - defining the damage state of damaged buildingsand other facilities with a particular emphasis on: the damage of the principalstructural elements and the entire structural system (including also estimation andinventory of nonstructural damages)

D functional damage assessment, i.e., the the usability of the buildings immediatelyafter an earthquake that essentially depends on the damage state of structuralelements and consequently on the integrity and post-event safety of the entirestructural system

According to the stated criteria, (Table 18, IZIIS – Skopje, 1979) buildings are given threeusability and five damage degree ratings.

The first two damage degree categories (Table 18) are allocated to usable buildings withsmall nonstructural damages and very isolated or negligible structural damage. These twodamage degrees (D1 and D2), assuming that the principal load carrying system is notaffected by the earthquake forces (damage state d1), when interrelated with usability cri-teria, are referred to as Damage/Usability category I (D&U-C-I).

The second two damage degree categories (D3 and D4) covering temporarily unusablebuildings with serious damage, but repairable structural systems (damage state d2) andextensive nonstructural damage when interrelated are referred to as Damage/Usability cat-egory II (D&U-C-II).

The third Damage/Usability category denoted by D&U-C-III, stands for unusable – severe-ly damaged, partially or totally collapsed buildings (damage state d3) for which it is moreeconomical to demolish since there is no technical or economical justification for theirrepair and strengthening (damage degree D5).

The damage degree categories grouped according to the post-event damage state of theprincipal load-carrying systems coincide with the usability categorisation of buildings. Theyalso define explicitly the state of damage of the components of the principal structural sys-tem with gradation levels formulated as:

D none (d1 = no structural damage)D moderate to severe (d2 = considerable structural and extensive nonstructural

damage)D total (d3 = partially or totally destroyed or collapsed structural system)

Besides the physical losses, the direct interrelations between the damage and usability cat-egories enable estimation of the functional losses. Loss estimates can be expressed eitherby the total number of buildings, or the corresponding total gross area which will be usable,temporarily unusable or unusable immediately after an earthquake of a given magnitude.

The specific loss of value for the considered types of buildings does not vary significantlywithin the damage categories. Due to construction peculiarities, the specific loss is mainlyassociated with damages to nonstructural elements, particularly if new structural systems

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such as RC frame buildings or buildings with RC shear walls are considered. It is also truefor masonry structures since, irrespective of the damage level of the main load-carryingwalls, the cost of their proper repair and strengthening, performed in full consideration ofworldwide construction standards and codes for repair and strengthening, will be approxi-mately the same. Therefore, through estimating the total gross area belonging to a partic-ular damage or usability category and applying proper structural-type-dependent specificcost estimators, it is possible to estimate the total economic losses associated with a givenclass of structures that should be expected if an earthquake of a given magnitude takesplace.

On this basis, a physical, functional or economic loss seismic risk models might be devel-oped in order to estimate the corresponding effects to be caused by earthquake occur-rence. The human casualty level is principally connected with the physical building dam-age, dominantly with damage degrees D3 and D4 (light injuries and injuries requiring hos-pitalisation) and D5 (injuries requiring hospitalisation, immediate medical attention anddeaths). With appropriate relationships interrelating physical damage with human casual-ty, then human casualty to mortality, reliable risk models can be developed for definingemergency needs (search and rescue, the health sector). Homelessness is another directoutput of the building risk models, being frequently defined in term of population thatshould be evacuated from buildings whose structural system has suffered damages corre-sponding to a damage state of d2 or higher.

The way a building deforms in an earthquake depends on the building type, as well as thebuilding damage patterns. As a broad categorisation one can group together types ofmasonry as well as buildings of reinforced concrete. While the behaviour of structures with-in the group is quite similar, due to structural differences and in particular due to the mech-anism of vertical load transport, their responses to earthquake differ radically from eachother. Consequently, their damage patterns are different and different criteria shall be usedfor estimating their post-event structural safety and integrity. Whilst the Table 18 is gener-ally applicable to all building of different structural typology, including industrial and otherbuildings, Table 19 provides more detailed damage descriptions relevant for masonry andRC buildings, as the prevalent structural typology in the Balkans, the Mediterranean andEurope.

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Damage and usability category

Usability category (U) Damage state (d) Damage

degree (D) Damage description Note

Table 18 Criteria for damage and usability classification of building structures

D/U-C-I

D/U-C-II

D/U-C-III

I. Usable

II. Temporaryunusable

III. Unusable

Without visible damage to structural elements.Possible fine cracks in the wall and ceiling mor-tar. Hardly visible nonstructural and structuraldamage.

Buildings classified in damage category1 and 2 are without decreased seismiccapacity and do not pose danger tohuman life. Immediately usable, orusable after removal of local hazards(cracked chimneys, attics or gablewalls).

Buildings classified in damage category3 and 4 are of significant decreasedseismic capacity. Limited entry is permitted, unusable before repair andstrengthening. Needs for supporting andprotection of the building and its surroundings should be considered.

Buildings classified in category 5 areunsafe with possible sudden collapse.Entry is prohibited. Protection of streetsand neighbouring buildings or urgentdemolition is required. Decision on dem-olition should be based on economicstudy considering repair and strengthen-ing as one of the possible alternatives.

Cracks to the wall and ceiling mortar. Falling oflarge patches of mortar from wall and ceiling sur-face. Considerable cracks, or partial failure ofchimneys, attics and gable walls. Disturbancepartial sliding, sliding and falling down of roofcovering. Cracks in structural members.

None (d1):Slight nonstructuraldamage, very isolated or negligible structural damage

Severe (d2):Extensive nonstructuraldamage, considerablestructural damagebut repairablestructural system

Total (d3):Destroyed, partially or totallycollapsed structural system

D1

D2

Diagonal or other cracks to structural walls, wallsbetween windows and similar structural ele-ments. Large cracks in reinforced structuralmembers: columns, beams, RC walls. Partiallyfailed or failed chimneys, attics or gable walls,disturbance, sliding and falling down of roof cov-ering.

Large cracks with or without detachments ofwalls with crushing of materials. Large crackswith crushed material of walls between windowsand similar elements of structural walls. Largecracks with small dislocation of RC structuralelements: columns, beams, RC walls. Slight dis-location of structural elements and the wholebuilding.

D3

D4

Structural elements and their connections areextremely damaged and dislocated. A large num-ber of crushed structural elements. Considerabledislocation of the entire building and roof struc-ture. Partially or completely failed buildings.

D4

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Damagedegree (D) General damage patterns Masonry buildings RC buildings

Negligible to slight damage: No structuraldamage, slight non-structural damage

Moderate damage:Slight structural damage, moderate non-structural damage

Hairline cracks in very fewwalls. Fall of small pieces ofplaster only. Fall of loosestones from upper parts ofbuildings in very few cases.

Cracks in many walls. Fall offairly large pieces of plaster.Partial collapse of chimneys

Fine cracks in plaster overframe members or in walls at thebase. Fine cracks in partitionsand infill.

Cracks in columns and beamsof frames and in structural walls.Cracks in partition and infillwalls; fall of brittle cladding andplaster. Falling mortar from thejoints of wall panels.

D1

D2

Substantial to heavydamage: Moderatestructural damage,heavy non-structuraldamage

Large and extensive cracks inmost walls. Roof tiles detach.Chimneys fracture at the roofline; failure of individual non-structural elements (partitions,gable walls)

Cracks in columns and beamcolumn joints of frames at thebase and at joints of coupledwalls. Spilling of concrete cover,buckling of reinforced rods.Large cracks in partition andinfill walls, failure of individualinfill panels.

D3

Very heavy damage:Heavy structural damage, very heavynon-structural damage

Serious failure of walls; partialstructural failure of roofs andfloors.

Large cracks in structural ele-ments with compression failureof concrete and fracture of rein-forcement bars; bond failure ofbeam-reinforced bars; tilting ofcolumns. Collapse of a fewcolumns or of a single upperfloor.

D4

Destruction: Veryheavy structural damage

Total or near total collapse. Collapse of ground floor or parts(e.g. wings) of buildings.

D5

Table 19 Classification of damage to masonry and RC buildings/Source: European Macroseismic Scale 1998/

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9. Human casualty and homelessnessEarthquakes are devastating to people as individuals, to families, to social and the eco-nomic organisation of the region affected and the country as a whole. Unquestionably, themost terrible consequence of earthquakes is the massive loss of human life.

The statistics recording earthquake effects include a wide range of earthquake-inducedcauses of human casualty and death. Although the principal cause of human casualty anddeaths is the collapse of buildings, there is a wide range of other causes of death and injuryofficially attributed to earthquake occurrence, ranging from medical conditions induced bythe shock of experiencing ground motion, to accidents occurring during the disturbance,epidemics among the homeless and shootings during martial law.

About 70% of fatalities and nearly 100% of injuries attributed to earthquakes are causedby the collapse of buildings (Spence and al., 1991). The greatest proportion of victims isdue to the collapse of masonry buildings. They are primarily weak masonry buildings(adobe, rubble stone or rammed earth) or unreinforced fired brick and concrete blockmasonry that collapse explosively at high intensities. These buildings make up a large pro-portion of the world’s current building stock, and are still prevalent in the Balkan regionmany other regions of Europe and throughout the World.

Increasingly low-income populations will continue to live in this type of structures, will con-tinue to live in and build them for the foreseeable future, in particular in rural areas wherethe administrative control of building type feasibility and construction quality ordinarily failsto be effective. Also, there are continuing changes in building typology in many countries,most of them at risk. Brick and block work and reinforced concrete framing are nowadayscommon materials and construction styles in even the most remote areas of the world.Reinforced concrete framed houses are generally safer, and they are less likely to col-lapse. However, they are also vulnerable, and when they do collapse they are consider-ably more lethal and kill a higher percentage of their occupants than masonry buildings.

When a powerful earthquake strikes a region of predominantly weak masonry buildings,90% of the buildings could be destroyed. If the earthquake occurs at night, catching mostpeople asleep in their homes, the mortality rate – the percentage of the population killed –in the towns and villages of the epicentral area could be as high as 30% (Table 20). Themorbidity rate – the percentage of the population injured and requiring some level of med-ical treatment – could be 60 to 80%.

Epicentral areas of large magnitude earthquakes (60-80%) may extend over hundreds ofsquare kilometres and many envelop a number of towns and tens if not hundreds of villages,depending on the population density and settlement patterns of the area. Denser popula-tion, or the epicentral area enveloping a major city, could push death tolls and numbers ofpeople requiring treatment far higher. Secondary disasters, such as major landslides, damcollapse or fire (much less likely with weaker masonry building types prevalent in Balkans,Mediterranean and Europe, but possible in areas of densely grouped timber-framed hous-ing like USA, Japan), could push death tolls and injuries an order of magnitude higher.

Table 20 Breakdown of typical injury ratios for a populationaffected by a severe-case earthquake scenario /Coburn and Spence, 1992/

Fatalities

Injuries requiring first aid/outpatient treatment

Injuries requiring hospitalisation

Injuries requiring major surgery

20 - 30%

50 - 70%

5 -10%

1 - 2%

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The majority of destructive earthquakes, however, will cause lower levels of injury rates, butwill put severe loads on medical treatment facilities (Fig. 14). Medical preparedness plansshould therefore be built around scenario calculations based on the building types likely tobe affected, population densities and settlement patterns, the size and character of earth-quakes expected in the region and medical facilities available in any understudy area.

From the above, the important role of the health care system is obvious in the post-disas-ter period. Hospitals and other health facilities are focal points for any community and, afterdisaster, have a vital role to play in attending the injured. Hospital buildings and facilities,however, can also be susceptible to the effects of natural hazards, in particular earth-quakes, substantially decreasing the community's is capacity to deal with problems in thissector during the emergency impact phase.

9.1 Epidemiology of earthquake casualtyWhen building collapses, not all the occupants are killed, injured or trapped inside. Manyare likely to escape just before the collapse and some, although injured are able to freethemselves shortly after. In high-rise buildings, escape from upper floors is unlikely beforethe collapse, and if the building collapses completely about 70% of the its occupants arelikely to be killed, at best injured and trapped. In low-rise buildings, that have apparently 20to 30 seconds to collapse, more than three quarters of the occupants may be able toescape before the collapse, and only one quarter can be considered a casualty toll.

A wide range of types and severity of injury are caused by earthquakes. A significant per-centage of injuries are not only a direct consequence of building collapse and may be theresult of many different earthquake-induced accidents. Some injuries are caused by non-structural building damage, such as broken glass or the fall of architectural ornament or thecollapse of parapet walls. But the majority of injures in a major earthquake are caused byheavy building damages and collapses.

Different types of buildings inflict injuries in different ways and to different degrees of sever-ity when they are damaged (Beinin, 1985). Huge amounts of dust are generated when abuilding is damaged or collapses, and dust clogging air passages and filling the lungs is aprimary cause of death in many building collapse victims (Coburn, 1992). In earthquakesaffecting weak masonry buildings, earth used as walling or roof material buries and suffo-cates the victim when collapse occurs (Coburn, 1992). There is also evidence that suffo-cation can occur from extreme pressure of materials on the chest preventing breathing.Many victims trapped inside a collapsed structure also suffer traumatic injuries from theimpact of building materials or other hard objects, and of these the most common appearto be skull or thorax injuries (Ashkahabad earthquake of 1948, USSR; Beinin 1985, anddata from Italian earthquake 1980, Alexander, 1984).

In some earthquakes, head injuries are by far the most common cause of death (Papayan,1983; Gueri and Alzate, 1984), but may constitute only a small proportion of the injuriesrequiring treatment among survivors. Multiple fractures of the spinal column are common-ly reported in many victims of some types of collapsed structures who were either stand-ing or lying down when collapse occurred (Beinin, 1985). Extensive spinal injuries of thissort appear to be less common in buildings with timber floors and associated more with‘harder’ building types with more rigid floors and roof slabs.

Another condition reported mainly in the collapse of large, concrete frame buildings issevere crushing of the thorax and abdomen, or the amputation of limbs by extreme pres-sure. Extreme pressure such as this is caused by large masses. But the most commontypes of injury caused in an earthquake are traumas and contusions caused by falling ele-ments like pieces of masonry, roof tiles and timber beams.

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Many more people tend to be injured in an earthquake than are killed. A ratio of three peo-ple requiring medical attention to every one person killed is typical (Ville de Goyet 1976;Alexander 1984), but this can vary significantly with the different types of constructionaffected and with the size of the earthquake. This is also true for light injuries requiring out-patient hospitalisation – typically there may be between 10 and 30 people requiring outpa-tient treatment for every person hospitalised.

Up to two thirds of patients are likely to have more than one type of injury. Most injuries arelikely to be minor cuts and bruises, with a smaller group suffering simple fractures and afew people with serious multiple fractures or internal injuries requiring surgery and otherintensive treatment (PAHO, 1981). Most demand for medical services occurs within thefirst 24 hours (Fig. 14).

In all disasters, earthquake-induced ones in particular, there are casualties. Generallythese casualties can be classified in three broad categories:

D alive and physically uninjuredD alive but injuredD dead

Emergency action is required to help and provide timely medical assistance to the ‘alivebut injured’ class of casualties in order to increase their chances of survival. This group ofinjuries can further be divided into the following three sub-groups:

D injured and trappedD injured and not trappedD injured but lost/not located.

While the problem of ‘injured and not trapped’ can efficiently be resolved or amortised bythe adequate emergency response of First Medical Aid, the Red Cross and other organi-sations capable of providing first aid, triage and professional medical help and services,

Fig. 14 Demands for medical services after an earthquake

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the problem of other two injury categories should sectorally be covered by specializedemergency services and organisations such as Fire brigades or civil protection. Both arecapable of providing professional search and rescue (SAR) activities because by definitionthey have well trained human resources, adequate specialised equipment and are alreadyorganised for efficient on-site operations.

The earthquake can create the following characteristic building-collapse injury classes thatpose serious threats to life and are the major cause of mortality of trapped victims:

• asphyxiation (due to dust caused by masonry or RC building collapse) and/orlung cementation

• severe arterial bleeding• severe head injuries• crash injuries• trauma injuries• crash syndrome

Table 21 Types of injury requiring treatment after an earthquake /Alexander 1985/

Fig. 15 Survival rate with time for victims trapped by building collapse

Soft tissue injuries (wounds and contusions)

Limb fractures

Head injuries

Others

30 - 70%

10 - 50%

3 - 10%

5%

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Other causes of trapped injuries mortality are:

• dehydration• hypothermia• starvation, etc.

The survival rate of trapped victims suffering from various categories of injury is different(Fig. 15). Suffocation (asphyxiation) is a major problem and allows only short time (1-1.5hour) for SAR operations and adequate medical treatment to be provided. Major blood lossallows about 12 hours, whereas severe scull injuries a maximum to 48 to 72 hours. Otherinjury categories in general provide longer survival time.

Survival time is a major parameter controlling the success of SAR operations. The suc-cessful SAR operations (victim extricated alive) are most efficient immediately after theearthquake strikes. With the passage of time efficiency decreases (Fig. 16) and after sev-eral days live rescues become sporadic (Fig. 17).

Fig. 16 Percentage of total live rescues as a function of time/1988 Armenia M6.9 Earthquake/

Fig. 17 Number of ‘live’ rescues in the first 5 days after the earthquake/1988 Armenia M6.9 Earthquake/

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9.2 Building collapse time and evacuationThe primary focus of most earthquake and other disaster protection programmes as wellas of all emergency services is to save lives, protect and accommodate part of the popu-lation left homeless. For loss estimation studies to be useful for planning and organisationof the emergency response, they need to include assessments of the probable levels ofhuman casualties (both deaths and injuries) and estimates on population that will be lefthomeless by the earthquake occurrence.

In the case of an earthquake, structures are dominantly subjected to horizontal and verti-cal inertial forces, whose magnitude is directly proportional to their mass. Time of exposi-tion of structures is relatively short, from tens of seconds (strong local earthquakes) to aminute or so, in the case of distant strong earthquakes with high magnitudes (Fig. 18).

The damage to the structure is “sudden” and is directly correlated to their seismic strength.The time needed for evacuation of buildings in principle is longer than the building collapsetime, so that the occupants are mainly indoors when the damage or collapse of the build-ing takes place. This is the basic cause of different kinds of injuries, as well as the reasonfor increased death rate compared to other types of disaster.

The short time span and impossibility of predicting the exact time of the earthquake occur-rence make it impossible to plan and undertake evacuation actions. It is very difficult tocarry out protection of the population as a preventive activity because one needs exactquantificators about the expected effects (place, magnitude, affected area, structural typesof buildings, population density and distribution according to structural types, estimatednumber of injuries/deaths), that are the basis for planning the acceptance of the conse-quences, preparedness and activities in the case of disaster.

Fig. 18 Evacuation time from multistorey building

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9.3 Building damage and casualtyThe building damage classification anticipates two structural damage degrees (D1 and D2,Tables 18 or 19) associated with negligible damage and loss of seismic strength of the prin-cipal load-carrying system, thus usable immediately after the earthquake occurrence.However, the damage degrees D3 to D5 (Tables 18 or 19) are associated with heavy dam-age, partial collapse and total collapse of the principal structural system. The buildingswhich are expected to experience these damage levels are of a significantly decreasedseismic strength (D3 and D4), unsafe for intended use, unless structural strengthening isperformed. Although recoverable at an economically justifiable cost, they have to be evac-uated, since they pose an increased risk to occupants, in particular during the period ofaftershock activity.

While the collapses (D5 damage level) are dominantly connected with human casualtiesand deaths, the D3 and D4 levels of structural damage are connected with a loss of func-tion and, if the building is of a residential use, with homelessness. However, if deaths orinjuries occur, they are caused incidentally due to panic or local instability of either non-structural elements or building content.

9.4 Estimation of human casualtyDeath tolls are highly variable from one earthquake to another. Consequently, the datadocumenting occurrences of loss of life in earthquakes are poor. During an earthquake thechaotic disruption and physical damage causes loss of life in many different ways – build-ing collapse, machinery accidents, heart attacks and many other causes. Some earth-quakes trigger collateral (secondary or follow-on) hazards like landslides, mudflows, fires,etc., which also cause loss of life and material property.

In some cases, collateral disasters like urban fires, mudflows, rockfalls and landslides, canlead to many more deaths than those caused directly by the earthquake. Collateral disas-ters of this type are extremely difficult to predict, but are fortunately rare. For the largemajority of earthquakes, deaths and injury are primarily related to building damage. Over75% of deaths are caused by building collapse (if secondary disasters are excluded, thebuilding collapse causes almost 90% of earthquake-related deaths).

In most countries highly destructive earthquakes constitute the most important part of earth-quake risk and are the focus of concern in earthquake protection measures and emergencymanagement planning. Casualty totals in large earthquakes can be predicted within certainconfidence limits using models of casualty occurrence based on building collapse.

A generalised casualty equation for the total deaths resulting from an earthquake can beexpressed as:

K = KS + K’ + K2

where:

Ks are fatalities due to structural damageK’ are fatalities from non-structural damageK2 are fatalities arising from collateral hazards

Variable K2 is rare, but where it occurs this is likely to dominate the total. K’ is dominant atlow levels of damage but it is highly variable and difficult to predict. Ks is consistent andthe controlling factor for most large and destructive earthquakes, and contributes a largepercentage of the total deaths from earthquakes.

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9.5 Casualties related to building collapseThe relationship between the number of people killed and the number of buildings which col-lapse, the lethality ratio, is the important parameter to determine. If this ratio is known, thenhuman casualties can be estimated from estimates of the number of collapsed buildings.

The casualty model is stated as a series of these factors which are applied to classes ofbuildings. For a class of building, or corresponding building (apartment) area, the numberof people killed can be expressed as:

Ksb = D5b x { M1 x M2 x M3 x [ M4 + M5 x (1 - M4)]}

where:

b is notation for a particular building classD5 (D5 = damage degree 5 of Tables 18 or 19) is the total number of collapsedstructures of buildings of type bFactors M1 to M5 are a range of modifiers to a potential mortality figure

Providing a total for all building types affected by the earthquake will give the total deaddue to building collapse, Ks.

9.5.1 Occupancy rate (Factor M1)Occupancy rate (M1) varies considerably from one place to another and can change sig-nificantly within a town or region in just a few years.

In low-rise residential building stock, the population per building (P/B) is equivalent to theaverage family size living in each house. In European cities, average residential P/B sizesare around 2 to 3. In cities with rapidly expanding populations, a large immigrant popula-tion or a shortage of building stock P/B ratios can be much higher and can increase ordecrease quite suddenly with changes of population movement.

Many rural areas associated with high death tolls in earthquakes (Iran, Turkey, Albaniansin Balkans /Kosovo, Macedonia, Northern Albania/, etc.) have very large family sizes - sur-veys show that 16-person households are not uncommon and average P/Bs’ in theseareas are around 8.

While the P/B is indispensable forhuman casualty risk assessments atenvironmentally unfavourable micro-locations for large-scale casualtyassessments such as municipal,national, regional multiregional, etc., itis feasible to replace P/B with a M1factor. The occupancy Rate (M1)defined as the number of occupantsper square metre of building area ofparticular building class, in a physicalsense can completely replace P/B,considering that D5 stands for a corre-sponding building area of buildingclass b and that vulnerability functionsare accordingly developed not pernumber of buildings, but in respect tothe corresponding building area.

Fig. 19 Occupancy at the time of earthquake (Factor M2)

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9.5.2 Occupancy at time of earthquake (Factor M2)The time of day that an earthquake occurs has long been known to affect the number ofpeople killed (Fig. 19). An earthquake occurring when a lot of the population is indoors killsmore people in the buildings that collapse. In societies spending a lot of time outdoors, forexample agricultural economies, the time of day can have a considerable effect on earth-quake mortality. Studies examining the comparative influence of time of day on lethalityratios show measurable variations of a factor of about two in deaths per building during theday in rural areas, mirroring typical occupancy patterns.

In urban areas and other types of community, more complex patterns of activity are found,with people moving from one building type to another, for example, from residential to non-residential, during the day. If non-residential buildings are more vulnerable, then death tollswill be higher when they are more fully occupied and vice versa. Studies (for example, urbanoccupancy surveys for radio companies) show that commuting activities considerablyreduce urban building occupancy during rush hours which may be reflected in earthquakecasualties during that time. Other temporal variations in occupancy occur seasonally (win-ter versus summer) and weekly (weekdays versus weekend). When detailed information onoccupancy cycles is not known for the understudy region and the relevant building typologyas well, the average occupancy levels for the whole day, week or year can be assumed.

9.5.3 Occupants trapped by collapse (Factor M3)Although there is little detailed information or statistics to quantify it empirically, it is clearthat not all the occupants that are inside a building when an earthquake occurs are trappedif it collapses. People escape before collapse, or the collapse of the structure is not total,or they are able to free themselves relatively easily by their own efforts.

In single storey structures, there is evidence that many people are able to get out of a build-ing before it collapses unless (as appears in the case for weak masonry buildings in theepicentre of strong earthquakes) collapse is instantaneous. In multi-storey structures fewerpeople are able to leave the building once shaking has started.

There is little documentation of the time it takes for buildings to collapse. A large magnitudeearthquake can have a minute or more of strong ground motion but the strongest ampli-tude shaking – the ones most likely to exceed the strength of the structures – happen rel-atively early. A ductile building may collapse over a period of several tens of seconds. Abrittle building may collapse more quickly. Tests of evacuation times (Fig. 18) show that

Building TypeSeismic Intensity (MSK Scale)

VII VIII IX X

Table 22 Estimated average percentage of occupants trapped by collapse(Factor M3, in %)

Masonry Buildings (up to 3 stories)

Non Earthquake Resistant

Earthquake Resistant

RC Structures

Near-field high frequency ground motion

Distant, long-period ground motion

5 30 60 70

- 10 30 60

70

50

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people cannot get out of a building from anywhere above the first floor in less than 30 sec-onds, even if they are capable of walking during the violent shaking. A reasonable assump-tion is that a certain percentage of occupants of the ground floor – for example, 50% for abuilding of fairly shallow plan depth, will be capable of escape; all other occupants of thebuilding will remain inside.

The main difference in M3 parameters between different buildings classified as collapsedis in the type and percentage of collapse. A reasonable assessment of M3 value (theentrapment rate) may be obtained by equating it to volumetric reduction of the building incollapse (Table 22). Buildings are classified as collapsed (D5) if they have more than onewall collapsed or more than half of the roof dislodged or failure of structural members toallow fall of roof or slab. Within this definition a range of types and extent of collapse canbe found, from one or two walls to complete structural disintegration. The volumetric reduc-tion in the building forms appears to be related to the extent of collapse to the entrapmentrate of occupants. In collapsed (D5) masonry buildings, volumetric reduction ranges from10% to 100%. The average extent of collapse at a location appears to be related to theground motion intensity (Fig. 20).

In weak masonry buildings closeto the epicentre of a large magni-tude earthquake the averagereduction in volume of collapsedbuildings can reach over 75%.Buildings classified as collapsed inlocations on the periphery ofearthquake-affected areas, and atlower intensities may have aver-age volumetric reductions of 30%or less.

Soil-structure interaction, storeyheight, structural characteristicsand location relative to other build-ings all influence the collapsemechanism and pattern of multi-storey reinforced concrete framestructures. The mechanism of col-lapse determines the volumetricreduction.

For reinforced concrete frame structures, four primary collapse mechanisms have beenidentified:

• ‘Bottom-up’ collapse starts from a failure in the ground floor, often caused bystiffness discontinuities, and often causes complete failure of the whole struc-ture (‘pancake collapse’ or 100% volume reduction). Average volumetric reduc-tions of all collapses classified as ‘bottom-up’ are around 75%.

• ‘Top-down’ collapse is a progressive collapse downwards from failures due tolarge deflections at the top of the structure, common in multi-storey ductilestructures. Top-down collapses are less severe with average volumetric reduc-tions of around 50%.

• ‘Pounding’ between adjoined buildings may cause collapse in some mid-levelstories with limited progression further. In average the volumetric reduction isabout 30%.

Fig. 20 Occupants Trapped by Collapse/Factor M3/

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• ‘Overturning’ of tall structures is often associated with torsional effects in cor-ner buildings, particularly those with a large proportion of openings on thefacades. The volumetric reduction can be extensive, averaging at about 75%.

The relative proportions ofthese collapse types amongmulti-storey RC structuresappears to depend on the char-acteristics of ground motion.Near-field, high frequencymotion appears to cause more‘bottom up’ types of collapse,with average M3 values ofaround 70% (Fig. 20). Long-period motions from distantearthquakes appear to causemore ‘top-down’ and ‘pounding’collapses, resulting in averageM3 values around 50%.

9.5.4 Injury distribution at collapse (Factor M4)People caught in building collapses suffer a range of types of injury (Fig. 21, Table 23). Aproportion of the occupants are killed outright when collapse occurs. This proportion(deaths at time 0 or T after the earthquake) is taken as the M4 factor in the casualty model.Others are injured to various degrees of severity. A number of injury severity scales havebeen proposed for quantifying earthquake injury epidemiological studies. One of the sim-plest and most useful to emergency managers is the four-point standard triage categori-sation of injuries. There is very little data to indicate the distribution of severity of injury tooccupants when a building collapses. However, studies back-figuring injury types and sur-vival times from mortality data of people retrieved from building collapses several dayslater suggest that in reinforced concrete structures, the M4 injury distribution is bi-modal,with most people being either killed or only slightly injured, with very few people badlyinjured in-between. By contrast, injury distributions in masonry buildings appear more uni-form, with high percentages of trapped victims having serious injuries.

Fig. 21 Injury Distribution at Collapse/Factor M4/

Triage Injury CategoryLow Strength

MasonryMasonry RC

Table 23 Estimated injury distribution at collapses (Factor M4, in % of trapped occupants)

Dead or unsavable

Life threatening cases needing immediatemedical attention

Injury requiring hospital treatment

Light injury not necessitating hospitalisation

10

20

30

40

20

30

30

20

40

10

40

10

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9.5.5 Mortality post-collapse (Factor M5)Those trapped in the rubble will die if they are not rescued and given medical treatment.Those who have serious injuries will die quickly. Less severely injured people can survivefor longer. The unaffected community usually rallies to the collapsed buildings and set towork to extricate trapped victims. Effective emergency activities will save the lives of manyof those trapped in building collapses who would otherwise have died.

Time is critical and death rates increase with every hour that passes. The M5 factor – theadditional mortality of trapped victims after collapse – is a measure of the effectiveness ofpost-collapse activities (Table 24). It is clear that in cases of extreme destruction, wherehigh percentages of the total population of a community are trapped in collapses (that is,M2 x M3 > 50%) the M5 factor becomes very high. The community itself loses its capabil-ity of rescuing its own victims, both because its manpower is greatly reduced and becauseit is psychologically and socially incapacitated by the disaster. In very high casualty earth-quakes (‘hyper-fatality events’) this appears to be a major factor in the escalation of casu-alty figures.

The number of people saved after collapse is a function of the capability of the rescue andmedical activities together with the survival time of those trapped in the rubble. Fig. 22presents indicative data on ‘fade-away’ time for people with different injuries and Table 24summarises aggregated survival rates of people retrieved in a number of earthquakes.Models of rescue and life-saving achievement have been proposed in which times are

Situation Masonry RC

Table 24 Percentage of trapped survivors in collapsed buildings that subsequently die (Factor M5, in %)

Community incapacitated

Community capable of organizing rescue activities

Community + emergency squads after 12 hours

Community emergency squads SAR experts after 36 hours

95

60

50

45

-

90

80

70

Fig. 22 Post-Collapse Mortality /Factor M5/

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assumed for the injury distribution to deteriorate and how manpower, equipment, searchtechniques, transport resources and other factors affect the extrication rates of victims.These models indicate that M5 is sensitive to improvements in rescue efficiency within thefirst 24 to 36 hours after the earthquake but that sensitivity diminishes extremely rapidlywith time. The logistical difficulties of mobilising rescue reinforcements into the affectedlocations within hours of en earthquake’s occurrence means that the potential for lifesav-ing in a stricken community relies heavily on the capabilities of the people on the spot.Specialist rescue teams arriving more than a few hours after the event are unlikely to makemuch of a difference to the overall death toll of a large earthquake.

Other factors known to affect fade-away time, and thus to influence M5, include the weath-er, temperatures at the rescue site, aftershocks, fire outbreaks and rainfall. Factors thataffect search and rescue effectiveness include building type (construction material), col-lapse type, manpower, equipment, skills, and other factors.

9.6 HomelessnessThe estimation of the homeless population is a straightforward follow up of the vulnerabil-ity and risk assessment for residential building use, that is,

NHb,i,j = (PDb3 + PDb4)i,j OCRb,i,jwhere:

NHb,i,j = homelessness in building class (b) by ownership sector (i)and urbanisation type (j)

(PDb3 , PDb4)i,j = functionally unfit housing areas of structural typology b byownership sectors and urbanisation type

OCRb,i,j = average occupancy rate (average M1) of building class (b) byownership sectors and urbanisation type

i = ownership sector (public, private)

j = urbanisation type (urban, rural)

The total number of homeless at the level of city/municipality/region (m) is a simple totalover the identified building typology (b), ownership sectors and urbanisation types, that is,

where NB is the number of different structural classes identified in thecity/municipality/region.

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10. Building triageIn recent years there have been many disasters worldwide where the fire brigades/reliefworkers/rescuers have been called upon more regularly to cope with the effects of structuralcollapse of buildings. These effects include the search for and the rescue of trapped victims.

10.1 Causes of collapseStructures may fail and collapse for many reasons. It is of utmost importance that thecause of the structural failure is discovered quickly, as this may indicate if further collaps-es are possible.

Some of most frequent causes of collapse are as listed below:

D fireD explosionD structural defectsD severe natural/geological effectsD blast damage

10.1.1 FireThe effects of the fire may weaken floors and supporting columns and the resultingincrease in pressure within a building may cause its partial or total collapse;

10.1.2 ExplosionExplosions can be grouped into the following three basic categories:

D Terrorist devices: can cause collapse of structure as in the “Grand Hotel” bomb inBrighton, England, or weaken the structure severely.

D Ignited gas explosion: leaking gas can reach an ignition source and ignite withexplosive force causing partial or full collapse.

D Explosion due to fire: flammable substances involved in a fire can ignite withexplosive force.

10.1.3 Structural DefectsInherent design defects can cause weaknesses to occur in parts of a structure which maysubsequently fail if stresses are applied, for example, fire, abnormal weather conditions,abnormal loading, heavy machinery, etc.

A building under demolition or renovation may also collapse if too many load-bearing wallsor floors are taken out without consideration to the effects on the other structural elements.

A 14-story apartment building collapsed on October 27, 1996 in Heliopolis (Cairo, Egypt)killing more than 100 people. Only a corner of the 25-years-old building remained stand-ing. The cause of the accident was attributed to combined effect of illegal erection of 7floors as well as to renovation work in one of the 40 apartments. Due to various structuraldefects, more than 100 buildings of different use have collapsed worldwide over the lastfour decades.

10.1.4 Severe natural/geological effectsEarthquakes, subsidence, tidal waves, high winds (hurricanes, tornadoes) etc, for exam-ple, can place sufficient stress on a structure to overload it and cause collapse, as seen inrecent years in Mexico, America, Iran, Japan, Turkey, Greece, Taiwan, etc.

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10.1.5 Blast damageBlast damage occurs in wartime situations involving heavy bombing attacks on towns andcities as during the Second World War and in recent years in Lebanon, Libya etc. It couldalso be the result of nuclear weapon explosions, or terrorist attack.

In 1995, a massive car bomb exploded outside the Alfred P. Murrah Federal Building inOklahoma City, ripping away the north face of the nine-storey structure. The explosion tookout three of the four columns of the north side of the building causing a progressive 'bot-tom-up' collapse that instantaneously had happened. One hundred and sixty-eight peoplewere killed. The bomb, made of ammonium nitrate and fuel oil, left a crater 6.5 metre wideand 2.5 metres deep.

On September 11, 2001, hijacked jetliners rammed into each of New York's World TradeCenter towers, toppling both in a hellish storm of ash, glass, smoke and leaping victims. Athird jetliner crashed into the Pentagon building in Virginia.

The hijacked planes were all en route to California, and therefore gorged with fuel. The first,American Airlines Flight 11, a Boeing 767 out of Boston for Los Angeles, crashed into thenorth tower at 8:48 a.m. Eighteen minutes later, United Airlines Flight 175, also headed fromBoston to Los Angeles, was flown into the south tower. The collapse of the towers causedanother WTC building to fall 10 hours later, and several other buildings in the area weredamaged or aflame. Numerous firefighters, police officers and other rescue workers whoresponded to the initial disaster in Lower Manhattan were killed or injured when the build-ings collapsed. Hundreds were treated for cuts, broken bones, burns and smoke inhalation.

The weight of a typical high-rise building is supported vertically by its columns. Thesecolumns commonly extend for the entire height of the building. The weight of each floor istransferred to the columns by a complex network of beams and slabs connecting to andspanning between the columns. Structural engineers design the beams, the columns, theslabs, and their connections to resist the anticipated loads.

The general belief is that towers did not collapse upon impact because they were original-ly designed to withstand enormous loads (hurricane-force winds and to survive the heat ofordinary fires). The impact of the aircraft did not take the buildings down; in fact one towerstood for about an hour after it was hit and the other stood for an hour and forty-five min-utes after impact.

When the airplanes were flown into the WTC towers a number of columns were severelydamaged. The damage from the impact, though significant, weakened the structure but didnot cause it to collapse. When the planes hit, they took out some of the structure, but thebuildings redistributed the loads and carried its weight. The surviving structural membershad to carry more load, so the fire did not have to heat them up as much as it would havenormally for them to collapse.

As steel heats up, it loses strength. A rule of thumb is that if steel is heated up to around600°C, it will lose approximately half of the strength of the member and eventually can nolonger carry the loads. Rather than impact itself, the intense heat of the resulting fire fedby great quantities of jet fuel further weakened the already damaged structural system.

This is what is believed to have led to the complete collapse of the crucial structural ele-ments in the impact area. The failure of these elements caused the portion of the buildingabove to drop, touching off a progressive 'top-down' failure as the entire structure col-lapsed onto itself.

Although the disaster at the World Trade Center was unprecedented in the devastatingcombination of forces produced by the impact of the airliner crashes and the burning jetfuel, the towers were able to stand long enough for tens of thousands of people to escape.

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Unfortunately, it appears that several thousand people did not escape the subsequent col-lapse of the towers.

10.2 Building construction classesAlmost all types of damaged buildings will contain voids or spaces in which trapped per-sons may survive for comparatively long periods of time. To know where these safe placesmay be, it is necessary to know the characteristics of various constructions. In consideringstructural damage (damage degrees D3 to D5, Tables 18 or 19) it is advantageous to dividebuildings into two classes:

D framedD unframed

10.2.1 Framed buildingsThe structural loads in these buildings, transmitted by the floors and roof, are supported bysteel or reinforced concrete skeleton or frame (RCF and RCSWS building classes,Table 17, Fig. 12) This type of construction is generally encountered in modern residentialand public buildings, office blocks, cinemas, hospitals etc. This type of construction has agreater resistance to collapse and, in general, failures which do occur are more localised.

However, if collapse occurs, it is spectacular. It is usually accompanied by a high casualtyrate and represents a major problem for search and rescue (SAR) operations.

10.2.2 Unframed buildingsIn these buildings walls carry all the structural loads (SM, BM and STM building classes,Table 17, Figs. 9 to 11). They are the traditional form of construction in many countries.Floors and roofs are supported by walls and typical brick and joist structure is usual.

Almost all dwelling houses, and many older large public buildings, are built in this way. Ifthe load-bearing walls fail along with column or floor beams, the result is an extensive col-lapse with a large area of debris. Void spaces can be formed by the support of strong struc-tural members, machinery or furniture. Persons can be trapped and can remain alive,sometimes injured.

10.3 Structural elementsThe structural elements of a building and their geometrical and mechanical relation to eachother are of major importance to the rescue teams when they have to consider the likeli-hood of structural collapse, of further collapse during the operation or under external forces(for example, the aftershock activity following a major earthquake event).

Building/dwelling house structural elements are defined as: ‘Any member-forming part ofthe structural frame of a building, or any other beam or column not being a member-form-ing part of a roof structure only’.

• a floor, other than the lowest floor of a building• an external wall• a separating wall• a component wall• a structure enclosing a protected shaft• a load-bearing wall or load-bearing part of a wall• a gallery; etc.

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The different elements of the structure are responsible for carrying the imposed loads.These loads are:

• dead load: which is the total weight of the building placed on the structural ele-ments and which is constant

• imposed load: which comprises all the contents of the building, including occu-pants, equipment, merchandise etc. These loads are variable and depend onbuilding use.

• wind load: being the forces imposed by the effects of winds• earthquake load: being the forces imposed by earthquake action, etc.

10.4 Signs of potential structural failureBuildings collapse due to different reasons. Collapse can occur under static and/or dynam-ic building loadings. The action of some of the loads is slow, while other are applied instan-taneously.

Buildings accumulate problems for a relatively long period of time. Then, they collapse sud-denly. If there are signs that something is going on, however, they should be understood.The signs to be aware of when assessing the possibility of structural collapse or further col-lapse are given below. Once these signs are understood, it is easier to suspect and recog-nise potentially dangerous conditions. However, it must be borne in mind that detection isnot always simple or readily obvious. Experience and skill are needed.

D Leaning walls. If a wall is leaning at the top more one third of its width at the base,there is a good chance it could collapse.

D Stepped cracks along brickwork. Such cracks can indicate a dropping of a foun-dation or support.

D V-shaped cracks. A ‘V-shaped crack in a wall can be a sigh of upward pressure. Thetop of the ‘V’ crack can cause a roof or floor support member to fail if the supportend is in line with it. If the ‘V’ is inverted, this can indicate movement downwards aswould be found if floors had dropped and support columns had failed.

D Sliding plaster and plaster dust. Portions of wall and ceiling plaster falling, slidingor cracking. Plaster duct clouds indicate a moving wall, floor or structure.

D Failure of whole or part of a roof. The restraining effect on walls is often removedwhen the roof has failed.

D Holes in floors. If alterations to buildings, such as cutting holes in floors, havebeen carried out after the structure has been built, the detrimental alterations mayhave weakened the floor with a consequent “knock on” effect.

D Floors bowing in centre. Indicates a weakening in the central part of the floorcaused by failure of the supports below.

D Cracks in padstone supports and rusting of external wall brackets. Padstones areoften used in warehouse structures to support floor members. They are some-times visible and exposed. Any cracks showing in or around them should be treat-ed with suspicion. So too should external iron wall brackets of the type used tosupport fire escape which are rusting, especially in old, unoccupied or derelictpremises. They should be treated with caution as these brackets may be partiallyrusted away and the extra weight of rescuers combined with vibration and move-ment may cause them to fail.

D Where fire is invoked, smoke issuing from cracks in masonry. Indicates greatinternal heat and pressure which can split the brickwork and lead to wall andmasonry collapse.

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D Distortion of door and window frames. Caused by wall and/or floor movements.Doors and windows may jam or not close when they worked perfectly well on anearlier occasion. Also glass window panes may shatter or crack suddenly, indi-cating floor or wall movement.

The above mentioned signs are pertinent to all modes of abnormality the building can reg-ularly be exposed to during its lifetime, such as overstressing due to improper design orinadequate upgrading in height, slow ground movements (landslide creep), differentialground settlements, prolonged flooding and weakening of the ground support, high watertable and suffosion of soil skeleton, volcanic ash overloading, etc.

Natural phenomena that impose sudden or dynamic loading, as well as blast (convention-al or nuclear) pressures cause rapid collapses. Inadequately designed buildings will cer-tanly collapse, but a number of them will sustain the adverse natural forces. To estimatethe possibility of sudden post-event collapses, the above mentioned signs should bechecked in order to ensure physical safety of relief workers as well as of non-evacuatedoccupants.

Different natural phenomena generate building collapses. The most critical are listedbelow:

D Earthquakes: produce horizontal ground movements which are amplified by thestructure itself, affecting the stability of the structure and often causing partial orcomplete collapse. They may also result in liquefaction, which induces failure orcollapse of the foundations. Heavy roofs may hasten the collapse of unstablestructures.

D Extreme winds produce horizontal surface loading, mainly in one direction, whichmay lead to partial or complete collapse. They also produce uplift loading on roofs;light roofs, if not designed to resist these forces and fastened securely, can be tornoff. This in turn will remove lateral restraint to the top of the walls and cause pro-gressive collapse of the building as a whole.

D Volcanic eruptions and tsunami have great force and will destroy or inundatebuildings in their path.

D Floods can cause buildings to collapse through scour or unequal pressure andcan cause gradual deterioration of the building and its foundations.

D Landslides produce directed loads, the angle of which can vary widely: the degreeof loading will depend on the speed and weight of the material involved.

10.5 Forms of collapsesThe construction of a building gives some indication of the way in which it may collapsewhen subjected to fire, explosion, earthquake, etc. Buildings of the same class and type ofconstruction collapse in much the same way and common factors are present. Collapsedbuildings can be categorised in much the same way as their victims are, and that is whythis is termed 'Building Triage'.

10.5.1 Masonry buildingsThe following collapse types are pertinent to masonry building types:

D internalD externalD total collapse

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Internal collapses Internal collapses (Figs. 23 to 26) are collapses of principal building elements (bearingwalls, floors, roof) taking place dominantly within the plane of the original, non-collapsed,building.

There are four ways in which a masonry building can collapse internally:

D pancakeD lean-to’ collapseD `V’ Collapse D ‘tent’ collapse

Pancake floor collapsePancake floor collapse (Fig. 23) is often mistakenly referred to as a total collapse. Fig. 23shows how a ruin generated by this type of collapse looks. When load bearing walls or anupper floor fails, the floor falls horizontally, or pancakes, upon a lower floor and the addedweight causes this and other floors to fall to a lower level, not necessarily all the way to theground level.

Voids are created by strong supports such as beams, machinery, home appliances, furni-ture, etc. and, although they may be small, this can be enough room to enable some occu-pants to survive.

The roof and upper walls will generally collapse on top of this void and from the outside themound of debris gives the impression of a complete collapse. The possibility that some ofthe occupants of the building could still be alive would seem remote to the untrained mind,but the rescue worker who understands the form of collapse would immediately suspectthe existence of a pancake void under the debris.

“Lean-to” floor collapse”Lean-to” floor collapse (Fig. 24) occurs when one of the supporting walls collapses or abeam fails at one end, as can be seen in the above figure. A triangular shaped void isformed under the floor where occupants may survive.

The floor may be supported against a wall and floor or it may be supported at the wall only,which is a far more dangerous situation.

Debris may cover the sloping floor completely but a careful reconnaissance and recon-struction of the mode of collapse should point out its existence.

Casualties may also be found among the debris on top of the sloping floor, but theirchances of survival are extremely low.

“V” - shape floor collapse“V” - shape floor collapse (Fig. 25) occurs when heavy loads or a collapse from aboveplace exceeding strain on the centre of a floor, which causes it to break in the middle. Thisis commonly associated with basement roofs. Voids are thus created at each end.Occupants, who were above the collapsed floor, are found in or under debris at the baseof the slope, but their chances of survival are quite low. Occupants below may be locatedin the void of the supported area.

“Tent” shape floor collapse“Tent” shape floor collapse (Fig. 26) occurs when the floor beams collapse near the outerwalls, but an interior bearing wall or steel girder remains intact. Voids are created with the‘tent’ where occupants can survive.

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Fig. 23 "PANCAKE" collapse Fig. 24 "LEAN-TO" collapse

Fig. 25 "V" collapse Fig. 26 "TENT" Collapse

Void

Void VoidVoid

Void

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External collapsesExternal collapses (Figs. 27 to 29) are mainly associ-ated with the external wall collapsing out and awayfrom the main structure. There are three ways inwhich an external wall can collapse:

D 90° angle collapseD curtain fall collapseD inward/outward collapse

90° Angle wall collapseThe 90° Angle wall collapse is the most dangerous asthe wall falls straight outward (Fig. 27) for a distanceequal to its full height.

Curtain-fall wall collapseThe wall comes straight down like a curtain cut loosenear the top and debris piles up near the base of thewall (Fig. 28).

Inward/outward wall collapseThe wall cracks horizontally in the middle, the top halfusually falling inward and the lower half falling out-ward (Fig. 29).

The listed internal/external collapse modes are dom-inantly characteristic for masonry buildings. However,‘pancake’ and ‘lean-to’ collapses can occur in RC insteel buildings when exposed to strong ground shak-ing.

Total CollapseTotal Collapse is the most severe form of structuralfailure where all floors have collapsed to the groundfloor or into the basement and all walls have col-lapsed onto the floors, making survival prospects verylow. However voids can still contain survivors.

Total collapse must not be mistaken for the 'pancake'collapse as there is a greater chance of survival in a'pancake' collapse and the wrong tactics could beemployed. It is essential that a full and thoroughreconnaissance be carried out.

10.5.2 Reinforced concrete buildingsFor reinforced concrete (RC) frame structures four primary collapse mechanisms havebeen identified:

D ‘Bottom-up’ collapse which starts from a failure in the ground floor. It is oftencaused by vertical stiffness discontinuities, and often causes complete failure ofthe whole structure (‘pancake collapse’). This is one of the most severe collapsemodes for victims, generating high mortality.

Fig. 27 "90° ANGLE" wall collapse

Fig. 28 "CURTAIN - FALL"wall collapse

Fig. 28 "INWARD/OUTWARD"wall collapse

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D ‘Top-down’ collapse is a progressive collapse downwards from failures due tolarge deflections at the top of the structure. It is quite common in multi-storey duc-tile RC structures. In respect to victim’s survival, the top-down collapses are lesssevere since they provide larger (by size and number) spaces.

D ‘Overturning’ of tall structures is often associated with torsional effects in cornerbuildings, particularly those with a large proportion of openings on the facades.The unfavourable behaviour of supporting soil masses (for example, liquefaction)or improper design of foundations can also lead to this collapse mode.

D ‘Ponding’ between adjoined buildings may cause collapse in some mid-level sto-ries with limited progression further. In, some cases ponding can cause even thetotal collapse of the entire building due to progressive building collapse down-wards, triggered by the dynamic impact of the failing upper building part.

All four collapse mechanisms can generate either partial or total building collapse.

10.6 Search and rescue demandsThe way a building has collapsed differentiates dramatically the search and rescue (SAR)demands in personnel, supplies and effort. Consequently, the SAR operations can begrouped in two general categories:

D rescue from a totally collapsed buildingD rescue from a partially collapsed building

There are some essential differences between the rescue operations relevant for totallyand partially collapsed buildings.

10.6.1 Rescue from a totally collapsed buildingThe time-consuming efforts and work required for finding and approaching the victims, whoare often unable to assist the rescuers due to their injuries, reduced mobility or uncon-sciousness. The great advantage of these rescue operations is that the possibility of therescue team getting injured is practically nil due to the ruin’s stability of volume, especial-ly for reinforced concrete or steel frame buildings.

10.6.2 Rescue from a partially collapsed buildingIn most cases partial collapses do not generate mass injuries /except in the collapsedstorey(s) or the part of the building/ and victims can co-operate and contribute to their res-cue. The whole operation is conducted at a fast pace. However, there is a risk of furthercollapses by additional overstressing of the remaining elements, or due to aftershock activ-ity following the main earthquake event, which can endanger the rescue team as well vic-tims being rescued.

10.7 Survival spots for trapped victims - voids and spaces Rescuers should always check the strongly supported areas, where spaces and voids willoften be found even though there is no evidence that victims may be trapped there.Remembering that the task is to locate and rescue live victims trapped in the shelteredareas under collapsed debris, the operation should be as extensive and as thorough aspossible.

The search area will be determined by the amount of damage, the type of collapse and thequestion of whether anyone was able to give a warning prior to the collapse.

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Likely survival points within a collapsed building are:

• sheltered parts of the building likely to have withstood damage• voids under collapsed floors• under stairs• beside chimney breasts (especially where there are cupboards)• in basements• in rooms which have not completely collapsed but where the entrance is

blocked• spaces around heavy machinery and furniture; etc.

10.8 Triage of building collapse victimsAlthough it is the duty of the medical teams present, an understanding of triage – systemfor sorting casualties – will greatly enhance the professional working co-operation betweenthe rescue services to a mutually successful end.

Triage is the evaluation and classification of multiple casualties for the purpose of estab-lishing priorities for treatment and evacuation. Sorting decisions may vary greatly depend-ing upon the situation and time, and vital supplies must not be wasted on hopeless injuries.

Irrespective of the cause of the collapse, according to the priority of emergency care, build-ing collapse victims are classified into four priority class categories (Table 25).

10.8.1 Class I priorityClass 1 priority category includes casualties in immediate danger from asphyxia, haemor-rhage or shock, who can be saved only by quick, efficient and energetic care. When life-saving measures such as clearing an obstructed airway or arresting haemorrhage can beaccomplished rapidly, such measures should be undertaken even when the conditions arehazardous for the rescuer.

This group will also include victims with severe arterial bleeding, cardiac arrest, respirato-ry arrest, respiratory problems such as airway obstruction or facial wounds, suckingwounds of the chest, shock resulting from major haemorrhage or multiple injuries, severehead injuries or damage to the skull, wounds exposing abdominal organs, poisoning, car-diac problems, and burns involving 15 percent or more of the body.

Priority Casualties' state

Table 25 Prioritisation of building collapse casualties

Class I

Class II

Class III

Class IV

Crash injuries

Victims whose chances of survival depend upon immediate emergency care(the critically injured)

Victims who need emergency care prior to transportation but whose survivalis not dependent on immediate care

Victims who apparently require simple emergency care or those who appearuninjured and only require observation

Dead or hopelessly injured victims whose chances of survival are slim evenwith ideal medical care

A special category of building collapse victims

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10.8.2 Class II priorityVictims in this group have suffered abdominal or thoracic wounds without respiratoryinvolvement or severe haemorrhage, amputations or severe wounds involving major bloodvessels of the extremities which have been controlled by application of compresses or atourniquet, head injuries without loss of consciousness or airway complications, spinalinjuries or major multiple fractures, burns involving 10 percent of the body area, and closedfractures and wounds.

10.8.3 Class III priorityClass III priority category includes slight injuries that can be managed by rescuers or evenby the injured person. In this group are: suspected fractures, sprains, strains, minorwounds and contusions; minor burns involving less than 10 percent of the body area; eyeinjuries; severe psychiatric or emotional problems. Although some victims in this categoryappear to be uninjured and emotionally stable, when time and facilities permit, they shouldbe removed to a medical centre for professional attention.

10.8.4 Class IV priorityRelief of pain and suffering of these casualties is all that is indicated. Time and effort mustnot be expended on victims in this group when it could be more effectively utilised on thosewho might live with immediate care.

10.8.5 Crush injuriesThis is a special category of building collapse victims, may even appear not to be physi-cally wounded, but were exposed to the pressure imposed by collapsed elements. Forcrush injuries sophisticated medical care is often needed prior to release. It is needed bothto assist in the freeing of the victim (during the operation of eliminating the pressure fromthe victims body) and to maximise his or her chances of survival.

Full preparation for successful structural collapse rescue includes medical teams whounderstand, and are equipped to deal with, the serious potential for crush syndrome, dustinhalation, and other problems encountered in these situations. The evaluation and treat-ment must begin prior to extrication, particularly when crush syndrome may be involved.

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11. Debris management and site vulnerability11.1 Debris geometry

The total collapse of a building creates debris of irregular shape that occupies an area larg-er than the ground floor area of the non-collapsed building. Depending on the intensity,direction and theroute of the seismicforce, buildings usual-ly collapse asymmet-rically, with extensionof the debris up to amaximum 2.5H, Hbeing the total build-ing height above theground (Fig. 30).

A methodology forestimation of the col-lapsed building debrisgeometry and quanti-ty was developedafter the 1963 Skopje(Macedonia, formerSFR Yugoslavia)earthquake. It wasintroduced in early1970s as a tool forplanning the blockagepotential of a cityurban transportationsystem, developmentof possible urban transportation system blocking scenarios, and plans for emergencydebris access and clearance. Revision of the methodology was made in the early 1980sbased on the data obtained from the 1979 Montenegro earthquake (FR Yugoslavia, formerSFR Yugoslavia).

For simplicity, it is usually assumed that a building collapses symmetrically on both axes(Fig. 30) with debris extension (d) of d = 0.5H and debris height (h) of h = 0.2H at theperimeter of the non-collapsed building. The assumed debris geometry (Fig. 30) and quan-tity (Table 26) are based on empirical and experimental data as well as on experience frompast earthquakes taking place in former Yugoslavia and worldwide.

Based on an average storey height (hs) of hs = 3 metres and average debris volume mass(Vm) for reinforced concrete and masonry buildings of Vm = 1.3 t/m3, the collapse of abuilding generates sv = 1.38 m3 or sm = 1.79t debris per square metre of a building grossfloor area of collapsed masonry building, and sv = 0.96 m3/m2 or sm = 1.25 t/m2 in the caseof a collapsed reinforced concrete building (Kovraz, 1985). The above figures are basedon typical building constructions in former Yugoslavia.

The amount of materials in modern European reinforced concrete buildings (Lauritzen,1995) is estimated at sm = 1 - 2 t/m2, or on average sm = 1.5 t/m2 of gross building floorarea, while in Japan, reinforced concrete structures generally use Vm = 0.6 m3/m2, whichresults in sm = 1.4 tonnes of concrete per square metre of a building gross floor area.

Fig. 30 Post-collapse debris geometry

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Abbr. Parameter Formula Description Unit

Table 26 Basic parameters of post-collapse debris geometry

Vm

Vd

H

Debris VolumeMass

Debris Volume

Building Height

d Debris Extent

Average volume mass ofdebris for reinforced concreteand masonry type buildings

Average volume of debris forreinforced concrete andmasonry type buildings

k - Looseness factor of thebuilding material after collapse

Building height above groundto top of parapet or eaves

Assumed extent of debris fromtotally collapsed (symmetrical-ly to both axis) building, meas-ured from its non-collapsedperimeter

Assumed average debrisheight along perimeter of total-ly collapsed building (debrisheight decreases to nil fromthe building perimeter to themaximum debris extent line)

The ground floor area of thebuilding itself including thearea coverd by its debris(under assumption that build-ing has totally collapsed)

Coverage of observed area(A) with debris

The overall debris aboveground level for analyzed area

The area average debrisquantity per unit of observedarea (A); (A = building grossfloor area or site area)

The average debris volumeper unit of observed buildinggross floor area

The average debris mass perunit of observed building grossfloor area

Vm=1.3Vm(m) = 1.10 - 1.30Vm(rc) = 1.30 - 1.60

Vd = k * Vm

k = 1.40

d=0.5*H

h=0.2*Hh(m) = 0.25*Hh(m) = 0.15*H

h Debris Height

Ad'=(a+2d)x(b+2d)Ad=Ad'/10,000

Ad Debris area

DPR=100 Ad/ADPR Debris plot ratio

Q Total DebrisQuantity

q=Q/Aq Specific DebrisQuantity

sv(rc) = 0.96

sv(m) = 1.38

sv Specific FloorDebris Volume

sm Specific FloorDebris Mass

t/m3

m3

m

m

m

m3

%

ha

m3/m2

m3/m2

t/m2sm(rc) = 1.25

sm(m) = 1.79

Average specific quantities for Average Building Floor Height hs =3 m /Kovraz, 1985/

(rc) - reinforced concrete(m) - masonry

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11.2 Debris classificationSuccessful debris management is dependent on appropriate classification of debris mate-rials, that is:

D reusable materials (bricks, blocks, roofing tiles, timber, metals, etc.)D rubble materials (masonry, stone and concrete)D waste materials (organic waste, paper, plastic, garbage, etc)D hazardous waste (asbestos, oil and chemical wastes, radioactive and radiation

contaminated materials)

11.3 Psychological issuesFrom a psychological point of view, debris management plays significant role in a commu-nity’s recovery from disaster. The clearing of debris from the street helps not only to assurethe effective and efficient access to other collapsed buildings and the restoration of the traf-fic system, but also contributes toward the overall psychological perception that things aregetting back to normal.

11.4 Environmental issuesWaste control has become great challenge for modern society due to a lack of disposalsites and limited natural resources. A lot of attention is devoted at present to debris recy-cling. Currently, most EU countries can economically recycle up to 80 to 90 percent of theconstruction and demolition generated debris. It is important, therefore, that debris be con-sidered a resource, and all opportunities for it’s recycling and re-use should be carefullyconsidered in order to save energy, natural resources, time and money. It is important tobe aware that the rapid response to emergency, and immediate and/or short-term activi-ties generated might not comply with long-term considerations and environmental policies(for example, uncontrolled handling and mixing of wastes is very difficult to be sorted outlater on). The most efficient approach, from the environmental point of view, is to pre-planthe post-disaster debris management activities and policies.

11.5 Debris-blocking potentialAn appropriate distance between buildings is one of the oldest methods of urban safetyagainst particular types of adverse hazard impacts, in particular against earthquakes andthe spread of urban fires. However, often the already understood effects and known prin-ciples are not properly implemented, and even intentionally violated. Urban areas devel-oped in such a manner possess an inherent potential for increasing the scale of problemsreceived by the adverse impact of environmental hazards (for example, spread of urbanfires), or can substantially decrease, even hamper, the effectiveness and efficiency ofemergency operations. An example is the potential for debris to block a street network.This is due to an unfavourable location of buildings in respect to each other, and to thestreet network itself. This was the case in the town of Golcuk, Turkey, where, following the1999 great Marmara Sea Earthquake, the emergency operations in some urban quarterwere completely hampered because access was impossible due to heavy collapses andoverlapping of ruins that extensively blocked some routes of the street network.

Table 27 presents a number of criteria used for urban planning and development of urbanareas in former Yugoslavia. While the presently used relationship provides excellent guid-ance for an effective approach to open-space urbanisation, it is also a good criterion toassess the potential and susceptibility of already developed urban areas to a particularproblem (for example, spread of fire or earthquake blocking potential).

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Source Distance between buildings - L (m) Expected effect

Table 27 Recommended distances between buildings in earthquake areas

DoxiadisAssociatesand ITPA(1965)

Kovraz (1985)

Krstic (1987)

Kovacev (1987)

Popovic (1990)

Lagorio (1990)

L=2.3*H

Case: equal buildings height orwhen the height of thetaller building is used

L = 2*H

Case: equal buildings height orwhen the height of thetaller building is used

L = 2*H

Case: equal buildings height

L = H

Case: equal buildings height

L = H1+20+H2

L = H1+10+H2

L = H1+H2

L = 0.5*H1+6+0.5*H2

L = H1+3+H2

L = 0.5*H1+3+0.5*H2

L = 0.5*H1+5+0.5*H2

But not less than the height ofthe taller building

L = 0.5*H1+0.5*H2

L = 1.5*H

The height of the taller buildingis used

L = 0.5*H1+0.5*H2

Provides 2 hours sunlight per day forsouth faced buildings for latitude 41°50'

Provides about 2 hours sunlight perday for south faced buildings for latitude 41°50'

Provides 6 hours sunlight per day foreast-west faced buildings for latitude41°50'

Provides 2 hours sunlight per day foreast-west faced buildings for latitude41°50'

Prevents fire spread and provides permanent access-egress

Prevents fire spread and is assumed toprovide permanent access-egress

Reduces fire spread and provides conditional access-egress

Postpones fire spread and providestime limited access-egress

Provides some access-egress in caseof debris extent: d=H

Provides some access-egress in caseof debris extent: d=0.5*H

Recommended distance between build-ings for earthquake areas in Croatia

Recommended distance between buildings in earthquake areas

Recommended distance between buildings in earthquake areas

Recommended for Mexico City afterthe 1985 earthquake

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For example, the relation:

L /m/ = 0.5 H1 + 0.5H2 + 6

proposed by Kovraz, 1985 (Table 27) recommends a building-to-building distance (L) thatwill assure slowing down spread of fire and providing time limited access.

On this basis, the fire-spreading potential of an urban quarter can be checked and ade-quate emergency preparedness elements derived. Considering that the dimensions of allbuildings in the quarter are known (a = length, b = width, H = height), as well as the areaof the quarter (Aq[m2]) itself, the necessary quarter area assuring the slowing of a firespread (Apq) can easily be calculated as:

Apq /m2/ = ∑∑ (an + Hn + 6) (bn + Hn + 6)

If Apq ≥ Aq the quarter satisfies the condition of slowing fire spread. Further screening canbe carried out for each individual building plot (n), A(q)n:

A(pq)n /m2/ = (an + Hn + 6) (bn + Hn + 6)

for defining whether all the individual buildings satisfy the stated criterion, or if individualbuilding risks exist.

On the contrary, if Apq < Aq, or A(pq)n < A(q)n, in the quarter, or on an individual buildingplot level, a considerable risk exists that the fire will spread from building to building, ifappropriate emergency measures are not taken in time.

Similarly, the blocking potential risks can be estimated for a street network in a quarter ofan existing urban settlement, and roads and streets classified in respect to access-egresscriteria as presented either in Tables 27 or 28. On this basis elements for emergency pre-paredness planning can rationally be developed. As well, the criteria and operation rulesfor on-site engagement of material and manpower resources can be established.

Class of access-egress road

Width of access-egress road (m) Description

Table 28 Classes of access-egress roads /Markov, 1982, 1983/

I

II

III

IV

> 6.0

> 3.5

< 3.5

Good access-egress in a case of adjacent buildingscollapsed

Fairly good access-egress in a case of adjacent build-ings collapsed

Relatively bad access-egress in a case of adjacentbuildings collapsed, can be cleared to achieve class II

Unacceptable access-egress in a case of adjacentbuildings collapsed; heavily covered with debris anddifficult to clear

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Abbr. UnitParameter Formula Description

Table 29 Site development indicators

Total area of the site covered by: (1) dwellingsand gardens, (2) half of the width of surroundingroads up to a maximum of 6 metres, (3) all roadswithin the site, (4) local shops, (5) nurseries, (6)kindergartens, (7) primary schools, (8) all openspace within the site, and (9) all other inciden-tal urban uses within the site boundaries

Part of the site area covered by: (1) dwellingsand gardens, (2) half of the width of surroundingroads up to a maximum of 6 metres, (3) all roadswithin the site, (4) local shops, (5) nurseries andkindergartens (only if part of residential build-ings), including part of the open space within thesite that belongs to them

Area of the site covered by residential buildings,including non-residential uses within or relatedto them (e.g., nurseries and shops within oradjacent to residential buildings)

Area of the site covered by non-residential build-ings, excluding area taken as part of residentialbuilt area

The overall residential floor space area, includ-ing non-residential uses within or related to res-idential buildings

The overall non-residential floor space areaexcluding non-residential floor space area takenas part of residential floor space area

The overall planned number of bed spaces onthe site

The site bed spaces number divided by thegross site area

The site bed spaces number divided by the netsite area

Indicates the level of gross site developmentwith emphasis on the relationship between theoverall floor space area and the gross site area

Indicates the level of net site development withemphasis on the relationship between the resi-dential floor space area only and the net sitearea

Indicates the level of gross site developmentwith emphasis on relationship between overallbuilt area and the gross site area

Indicates the level of net site development withemphasis on relationship between residentialbuilt area only and the net site area

Site gross area

Site net area

Residentialbuilt area

Non-residentialbuilt area

Residentialfloor area

Non-residentialfloor area

Bed spaces

Gross residen-tial density

Net residentialdensity

Gross floorspace index

Net floor spaceindex

Net buildingplot ratio

Gross buildingplot ratio

ha

ha

ha

ha

ha

ha

bdsps

bdspsha

bdspsha

%

%

BDSPSSGA

BDSPSSNA

RFA+NRFASGA

RFASNA

100*(RBA+ NRBA)SGA

100*NRBASNA

SGA

SNA

RBA

NRBA

RFA

NRFA

BDSPS

GRD

NRD

GFSI

NFSI

GBPR

NBPR

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11.6 Site vulnerabilitySite vulnerability assessment (of the site itself, not the vulnerability of the individual build-ings themselves) against natural or man-made hazards is based on:

• building vulnerability assessment in respect to building materials used and con-struction type (Table 17)

• floor space indices (parameters GSFI and NSFI, Table 30), building plot indices(parameters GBPR and NBPR, Table 30)

• site layout (parameters SGA, SNA, RBA, NRBA, RFA, NRFA, BDSPS, GRD,NRD; Table 30)

• building heights, emergency access-egress routes, open spaces, etc.

The building collapse hazard is the main factor of the analysis, as the collapse of a build-ing creates debris of either regular or irregular shape which takes up an area larger thanthe ground floor area of the non-collapsed building. With the increase of the amount ofdebris and with an increase of urban area covered with debris, the vulnerability of the siteincreases.

For the purpose of urban planning and design (mitigation phase) as well as emergencypreparedness, the criteria for site vulnerability analysis, based on the building collapsegeometry, are:

D the building collapse (debris layout) plan of the urban site (indicating total sym-metrical collapse of all buildings on the site with extent of the debris indicated)

D relationship between height of a building and debrisD debris quantity (based on the total and specific quantity of debris)

Using the building collapse (or debris distribution) plan it is possible to evaluate the levelof site coverage with debris, that is:

• gross and net debris indicators, (Table 31) - areas /GDA and NDA/, plot ratios/GDPR and NDPR/, volumes /GSDQ and NSDQ/, masses /GSDM and NSDM/(Table 31)

• required refuge space area (RSA, Table 31) for predefined refuge space provi-sions (RSP, Table 31)

• expected gross and net debris areas (GEDA and NEDA, Table 31)• gross and net debris overlapping ratios (GDOR and NDOR, Table 31)• the provision for access-egress, possible location of refuge spaces (where the

population can be temporarily evacuated without risk to their life from follow-onearthquake hazards, such as fire, or possibility of collapse of partially collapsedbuildings during the aftershock activity) etc.

According to the recommendations of former Yugoslav Civil Protection, areas appropriatefor refuge shelter are considered to be those located at least two building heights from thesurrounding buildings.

The percentage of coverage of observed area with debris (debris plot ratio = GEDA/SGAor NEDA/NGA) can be used as one criterion (Table 32) to estimate the site vulnerability.Building and debris height, as well as specific debris quantities (GSDQ, NSDQ, GSDM andNSDM; Table 31) can also be used to estimate the site vulnerability (Table 34) as well asto plan the necessary mechanisation for emergency clearance. The debris extent or heightcan also be used for the same purpose and checked against criteria presented in Table 33.

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The floor space indices, Table 29: parameters GFSI and NFSI might also be used as sitevulnerability indicators. In earthquake prone areas they should be between 1 and 1.2, astheir further increase leads to increased vulnerability, to that extent an index above 2 is notacceptable for safety reasons.

The discussed technique is based only on visual evaluation of the effects of the debris lay-out on the site vulnerability, but it does not try to quantify it. In order to improve this, a newparameter should be introduced – the debris overlapping ratio – indicating the level ofdebris overlapping among all buildings on the site (greater overlapping means greater sitevulnerability). The debris-overlapping ratio is of essential importance for evaluation of pos-sible blocking potential as well as planning of effective and efficient emergency debrisclearance operations following a catastrophic earthquake.

Parameter1965 Skopje Urban Plan

Markov(1982,1983)

Zakic(1982)

1985 Amendments

Vlcevski(1984)

Krstic(1987)

Table 30 Recommended development control standards for earthquake prone areas in Skopje and Former Yugoslavia

Gross residentialdensity (low rise)BDSPS/ha

Gross residentialdensity (mid - andhigh-rise) BDSPS/ha

Maximum gross residential density BDSPS/ha

Net residential density (low -rise)BDSPS/ha

Net residential density (Mid- andhigh- rise) BDSPS/ha

Maximum net residential densityBDSPS/ha

Floor space index inresidential areas

Floor space index inmixed areas

Building plot ratio forresidential areas (%)

Building plot ratio formixed areas (%)

Building plot ratio forcommercial areas (%)

Building plot ratio forindustrial areas (%)

< 150

< 300

< 400

< 200

350-500

< 1.00 (< 0.33)4

< 2.00 (< 0.33)4

< 30 < 204

< 40 < 204

< 50 < 204

< 60 < 204

< 150

240-280

< 300

0.36-0.42

0.65-0.75

< 2001

< 3002

< 3503

< 500

< 30

< 40

1.00-1.20

20-30

60-120

150-250

250-280

< 400

1 - for towns with population of up to 10,0002 - for towns with population of up to 100,0003 - for towns with population of more than 100,0004 - for prevention of collateral earthquake hazards, such as fire

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Abbr. UnitParameter Formula Description

Table 31 Calculation of site vulnerability assessment indicators

The overall ground floor area of all analysedbuildings on the site, including the area coveredby their debris under assumption that allanalysed buildings on the site have totally col-lapsed as calculated from the site layout plan

The overall ground floor area of all analysed res-idential buildings on the site, including the areacovered by their debris under assumption thatall analysed residential buildings on the sitehave totally collapsed as calculated from the sitelayout plan

Indicating coverage of gross site area withdebris

Indicating coverage of net site area with debris

Average building height for overall site

Average building height for residential part ofsite only

The debris volume above ground level of grosssite area

The debris volume above ground level of netsite area

The debris weight above ground level of grosssite area

The debris weight above ground level of net sitearea

Area where residents are assumed to be pro-tected from injuries resulting from buildings col-lapse or damage; boundaries of the refugespace area are determined by distance of 2*Hfrom its perimeter to the adjacent buildings

Refuge space provision per planned number ofbed spaces on the site

The sum of all individual buildings debris areason the site regardless of the relationship

The sum of all individual residential buildingsdebris areas on the site regardless of their rela-tionship

Indicating the level of debris overlapping amongall buildings on the site (greater overlappingmeans greater vulnerability)

Indicating the level of debris overlapping amongall residential buildings on the site (greater over-lapping means greater vulnerability)

Gross debrisarea

Net debrisarea

Gross debrisplot ratio

Net debris plotratio

Average grossbuilding height

Average netbuilding height

Gross specificdebris quantity

Net specificdebris quantity

Gross specificdebris quantity

Net specificdebris quantity

Refuge spacearea

Refuge spaceprovision

Gross expect-ed debris area

Net expecteddebris area

Gross debrisoverlappingratio

Net debrisoverlappingratio

ha

ha

%

%

Stories

Stories

m3/m2

m3/m2

t/m2

t/m2

ha

m2

bdsps

ha

ha

%

%

100*GDASGA

100*NDASNA

RFA+NRFARBA+NRBA

RFARBA

0.96*GFSI

0.96*NFSI

1.25*GFSI

1.25*NFSI

10,000*RSABDSPS

Σ Ad

Σ Adr

100* (GEDA-GDA)GEDA

100* (NEDA-NDA)NEDA

GDA

NDA

GDPR

NDPR

AGBH

ANBH

GSDQ

NSDQ

GSDM

NSDM

RSA

RSP

GEDA

NEDA

GDOR

NDOR

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Debris plot ratio (%) Site vulnerability

Table 32 Site vulnerability by debris plot ratio /Kovraz, 1985/

< 40

40 - 70

70 - 90

> 90

small

average

increased

high

SDS at Urban Environment (m3/m2) Site vulnerability

Table 34 Site vulnerability by specific debris quantity /Kovraz, 1985/

< 0.4

0.4 - 0.7

0.7 - 1.1

1.1 - 2.0

>2.0

small

average

increased

high

very high

Debris plot ratio (%)

Stories m Extent Height

Debris (m)Site vulnerability

Table 33 Site vulnerability by debris extent and height /Kovraz, 1985/

2

4

5

8

16

21

small

small

increased

high

very high

very high

1.6

2.8

3.4

5.2

10.0

13.0

4.0

7.0

8.5

13.0

25.0

32.5

8

14

17

26

50

65

Specific Debris Quantity (SDS) = Debris height evenly distributed to the site

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12. Some Societal and psychological issues of emergency response12.1 Behavioural disaster myths

The widely held beliefs given below are all wrong. They are not correct when applied to adisaster and on the basis of the evidence available, they are likely to be wrong whenapplied to a civilian population in wartime. Strangely, however, even those with disasterexperience tend to believe some of these myths.

In fact, evidence shows that in the wake of disaster the first thing people do is try to help theirfamilies; the second thing is to assist their neighbours. The idea of dazed, shocked victimswandering about helpless is not true, despite what people might say or think after the event.

For example, a woman was interviewed after a mudslide had led to her evacuation. Thiswoman explained how she felt so upset at the time that she: “ran around screaming in cir-cles”. On further investigation, however, it was discovered that she: woke her husband, ashift worker, who was sleeping; she alerted the emergency agencies; she warned herneighbours; and she packed and loaded the car and drove herself and her husband tosafety. She therefore acted rationally and constructively and, although she might well havescreamed, she was certainly able to cope.

In fact, many disasters, earthquakes in particular, provide abundant evidence on contrary:

“ … The initial search and rescue was unorganised and mostly performed by theearthquake survivors themselves, who frantically tried to rescue family members andneighbours tangled or covered by the debris. These volunteers were not trainedemergency personnel, and their efforts were limited. Scarce or unavailable heavy lift-ing equipment, no search dogs, and physical and mental exhaustion exacerbatedTurkey’s most costly natural disaster.” [Marmara, Turkey Earthquake of 1999,MCEER-00-0001]

As the previous stories suggest, panic rarely occurs in disaster. People may be worried,nervous, upset, anxious, even excited, but they do not panic. They do not run off leavingtheir family and friends behind. Even in a major industrial incident involving explosives,there is evidence of flight, but not panic. It is easy to confuse flight with panic, but the for-mer is often based on quite rational considerations, that is, that it is necessary to flee inorder to avoid danger. Conversely, people often stay put in face of danger, reluctant torecognise the most severe threat. Although this may not be considered rational, it demon-strates people’s calm in the face of adversity.

In distress, people with emergency responsibilities stay on the job even if it costs them theirlives. Even those worried about their families and knowing them to be in danger, put dutyfirst. There are no documented cases of role abandonment in the face of disaster. In

Myth No. 1: In a disaster it is widely believed that those affected – the vic-tims – become dazed and shocked and are unable to cope.

Myth No. 2: People panic, and run from danger, acting irrationally. It is sup-posed that people – even those with emergency responsibili-ties - will leave their posts to look after their family. Family tiesand concerns take priority over duties.

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Halifax (Nova Scotia, Canada), for example, when the French munitions ship the MontBlanc exploded in the city’s inner harbour devastating part of the city (the explosion wasso severe that the impact was later studied by those trying to understand the potentialimpact of an atomic bomb), the fire-fighters carried on despite the knowledge that their sen-ior commanders had been blown up as they were attacking the fire. Also a telegrapher diedwhile warning an incoming train. Similarly, in Ottawa, when there was a hotel fire at theBeacon Arms Hotel, the switchboard operator stayed at her post warning guests until shedied. Often the real problem in a disaster is “convergence”; that is, running toward thescene of disaster. Those outside the impact area tended to come in frequently in numberstoo great to be useful. This results in an overload of response with too many people andequipment and too much information being passed around. It is therefore not surprisingthat in the wake of disaster the telephone system frequently overloads and collapses.Everyone wants to talk at once. Past emergencies have shown this to be true: after theZeebrugge ferry disaster (off the coast of Belgium), the number of persons seeking infor-mation created serious communication problems; and in the wake of the 1987 storms insouthern England, the overload on the telephone system was so extreme that public ser-vants had to leave their offices to use pay phones.

In 18 years of studying disasters, and direct experience of some 50 incidents, the authorof the paper the extracts are taken from [J. Scanlon, Carleton University, Ottawa, Ontario,Canada], has only come across three cases of looting. One involved some people in a sea-port picking up goods spilled from a damaged vessel, just as has always been done whena ship is wrecked on shore. Another case involved two people collecting another person’svaluables in a devastated trailer park after a tornado. (They did it so openly that they werearrested within minutes of starting.) And the third example involved theft of other people’spossessions, including guns, after cyclone Tracey in Darwin, Australia. Looting happens sorarely that it cannot be viewed as a serious problem after disaster. In the wake of disaster,there are often reports of looting; victims or sometimes relatives of victims, in return to adamaged area to retrieve ‘missing’ valuables; others see known faces and report looting.Officials, worried about looting, take exaggerated precautions giving orders to shoot loot-ers. These actions are ill-founded as the evidence of looting is negligible.

This is also largely a myth. TV coverage after a Mexican earthquake (Michoacan, 85)showed various international search and rescue teams assisting the Mexicans. However,available evidence shows that those who were rescued were rescued by Mexicans, large-ly by those “on the spot” or close when the earthquake occurred. There may have been afew individual, dramatic rescues (largely for the benefit of the television cameras) when for-eigners arrived, but local people did the bulk of the work, as you would expect. This maybe difficult to accept but organisations do not always fare too well in disasters, especiallyin the early stages.

Myth No. 3: Disasters are also believed to bring anti-social behaviour suchas looting, and crime rates rise.

Myth No. 4: It is felt that these problems must be dealt with by the calm,cool, collected outside organisations, which will move in andefficiently resolve the difficulties; and that the affected popula-tion will be helped by a fully organised and calm response.

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“ … The emergency management response effort got off to a slow start for the firstseveral days. … Command and control at all levels was severely limited during thefirst day. … The sheer size of the disaster – covering a very large, heavily populatedurban and industrial area – combined with the initially limited national and local insti-tutional and organizational response, detracted from a more efficient timely start forthe emergency phase of search and rescue management. …

A national volunteer search and rescue ream (AKUT) began working in Istanbul with-in 24 hours of the event, and continued to work after all foreign teams had departed.Foreign search and rescue teams came from Algeria, Austria, Azerbaijan, Belgium,Bulgaria, Canada, Denmark, Finland, France, Germany, Greece, Hungary, Israel,Italy, Japan, Kuwait, Norway, Poland, Russia, Spain, Sweden, Switzerland, UnitedKingdom and USA, with several arriving on Day 1. A reported 50,000 Turkish soldierswere assisting in the search and rescue by Friday, August 20 (Day 4). Intensive res-cue efforts lasted through Day 4.

Media reports estimated that 1,000 foreign search and rescue people were in Turkeywithin the first 48 hours. Several teams had technical equipment and dogs – butmany did not. Based on a variety of news reports, it appears that the approximately1,000 foreign search and rescue team members and staff (some with dogs and high-ly technical listening devices), along with 50,000 Turkish solders, and dozens ofAKUT volunteers saved 17 people. This small number of rescued victims contrastswith Turkish television, which reported on August 29 that 65 foreign rescuer teams,made up of 2,700 specialists and 109 search dogs, saved 621 lives. Even more con-troversial were media reports on August 29, which announced that the Army had res-cued 40,646 victims “from the rubble”. …” [Marmara, Turkey Earthquake of 1999,MCEER-00-0001]

Disasters often create an overload on communication systems, which prevents themfrom functioning effectively. Without communication, organisations have difficulty inassessing what is going on and, as a result, cannot organise an appropriateresponse.

“ … It was widely reported that President Demirel and Prime Minister Ecevit wereunable to communicate with Ankara from Istanbul for up to four hours. Evidentlythere was no operational communications back-up. … ” [Marmara, TurkeyEarthquake of 1999, MCEER-00-0001]

Disasters cause damage. They knock out power systems and telephone lines, sweepaway bridges and tear apart roads. Sometimes it is very difficult for agencies to moveabout. They may know where they want to go, but they cannot get there. Also, in the wakeof disaster, the victims tend to move – the injured go to hospital, the homeless find some-one to stay with, those injured and merely passing by, helps out and disappear. Hospitalstherefore have no idea where their patients are coming from. Volunteer agencies, such asthe Red Cross, are unable to assess who needs help. Finally, immediately after disaster,agencies are not always on the scene.

It is a myth that outside agencies, especially volunteer agencies are unquestionably wel-comed by the victims. Samuel Henry Prince [an Anglican priest studying the response tothe explosion for his PhD at Columbia University, New York] noticed that after the Halifaxexplosion, Haligonians resented the strangers (Americans who had come to help) and the

Myth No. 5: It is thought that everyone welcome this help especially fromoutside volunteers.

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way they did things. He also noticed that various religions, for example Roman Catholicsand the Salvation Army, did not work together. Others have since noticed the same thing.People prefer, if possible, to take care of their own needs. Local volunteers are welcome,but outside help is often resented.

“ … The Minister of Health, Mr. Osman Durmus, called for terminating all foreignassistance and stated “we do not need any help” during a widely viewed and pub-lished press conference on August 22. His comments were strongly criticised by theTurkish people who were expressing their gratitude to the international and nationalrescue teams …

… The press reported that all foreign teams were to leave Turkey by Wednesday,August 25. Most of the foreign teams had departed by August 24. … “ [Marmara,Turkey Earthquake of 1999, MCEER-00-0001]

Deaths Injury

Reported CasualtyDay Date SAR team Rescues

Table 35 Marmara earthquake, 1999: Efficiency of organised SAR activities andcasualty reports

/Source of Data: The Marmara, Turkey Earthquake of August 17, 1999 - Reconnaissance Report, Technical Report MCEER-00-0001, March 23, 2000/

1

2

2

3

3

4

5

5

5

6

7

8

9

10

Earthquake: August 17, 1999 00:01:38.56 (UTC) - 02:01:38.56 Local Time

August 18

August 18

August 19

August 19

August 20

August 21

August 21

August 21

August 22

August 23

August 24

August 25

August 26

September 1

October 13

3,7891

10,0091

12,0002

18,0001

13,0093

>14,0001

17,1184

16,0001

38,0002

26,6303

25,3761

>40,0004

AKUT

From Israel

From France

From Switzerland

From Hungary

From Israel

From France

From Turkey

From Turkey

From Israel

2 rescues

2 (to military survivors)

2 (16 year-old girl and a man in Yalova)

2

1 (3 year-ld girl in Izmit)

1 (10 year-ld girl in Cinarcik)

1 (95 year-ld woman near Cinarcik)

3 (19 and 10 year-ld sisters inGolcuk, 23 year-ld man in Yalova)

1 (45 year-ld woman in Golcuk)

1 (25 year-ld man in Korfez)

1 (4 year-old boy)

1 - Media reports2 - Report of Turkish Government3 - Revision of casually by Turkish Government. Besides the numbers presented,

the statement included the phrase: …"with thousands missing"4 - Statement of Agence France-Presse, October 14, 1999

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Why are we all so inaccurate in our beliefs? The available evidence suggests one clear cul-prit – the mass media. News reports invariably cover any evidence of panic, the dazed cry-ing victims – not those who went about their business helping others, or to interview well-organised officials saying how they went about a constructive rescue campaign.

12.2 Disaster work and psychological traumaWhile there has been a growing awareness of the psychological adjustment problems thatcan be faced by survivors in the aftermath of a disaster, the problems experienced by pro-fessional helpers have until recently been neglected. The psychological plight of disastervictims has been fairly well documented over the years, and as disaster contingency plan-ning has become more systematic, a number of manuals and handbooks for the mentalhealth care of victims have been produced. However, information has been lacking on thepsychological problems that can be faced by the many professional helpers who have towork in disaster situations – the personnel who are deployed from the local fire services,police forces, hospitals, civil protection, etc.

It is perhaps easy to assume that professional helpers are “experienced” in the kind of workwhich faces them after a disaster, and that they should be quite capable of carrying outtheir tasks with suitable detachment. It takes little reflection, however, to realise that,although disasters appear to occur quite regularly when viewed from a national perspec-tive, any particular group of helpers is unlikely ever to become very experienced at deal-ing with them. At each disaster, there will probably be a majority of professional helperspresent who, whatever their prior experience, will never before have encountered death,suffering and devastation on such a scale.

12.2.1 Nature of psychological traumaPsychological trauma refers to the severe cognitive-affective disruption which can followthe experience of certain kinds of extreme events – including those where there is no phys-ical injury. The word currently tends to be reserved for describing the impact of eventswhich are outside the range of usual human experience, and so would not normally beused in connection with more common negative life events such as bereavement, chronicillness, burglary, business failure or material breakdown, disruptive though such events canbe. Examples of potentially traumatic events would include violent crime (for example,rape, assault), natural disasters (such as, volcanic eruptions, earthquakes), accidental dis-asters (for example, serious transportation accidents, airliner crashes, large fires) anddeliberate disasters (for example, terrorist attacks, military attacks). The events can beexperienced alone (for example, torture), in the company of group of people (for example,hijacking), or in a community (for example, a massacre in town). Clearly, some kinds ofevents will have a greater impact than others. For example, being subject to deliberate,man-made destruction or suffering is likely to produce very severe effects.

For those professionals who are significantly affected by disaster work on any particularoccasion, the psychological adjustment problems will range from those that are transitoryand self-correcting to longer-term, incapacitating, and which meet the criteria for psycho-logical disorder. When considering these more serious adjustment problems, the concept

The Chapter 12.1 is arranged by extensive use and quotations from the following references:Scanlon J., “Planning for Peace and War Emergencies – learning from 70 Years of Disaster Research”,Disasters Management, Vol.1 No. 2, 1998; Professor Scanlon is [was] Director of the EmergencyCommunications Research Unit, Carleton University, Ottawa, Ontario, Canada. The paper, from which theextracts are taken, is based on a presentation given by Professor Scanlon in July 1988, to the Association ofCivil Defence & Emergency Planning Officers, Blackpool, England.The Marmara, Turkey Earthquake of August 17, 1999 – Reconnaissance Report, Technical Report MCEER-00-0001, March 23, 2000.

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of psychological trauma becomes relevant. It provides a useful basis for understanding andmanaging the possible psychological sequences of disaster work.

Many personal and socio-environment factors will mediate the initial and subsequentimpact of an extreme event. Some of characteristic factors are:

• prior experience of similar events• current constitutional characteristics• preparedness for the event• the availability of social support

One of the most basic factors will be the meaning that the event has for the person. It isquite possible to learn to view danger, human emergencies, suffering, mutilation and deathin a psychologically detached fashion. Indeed firemen, police, emergency transport staffand medical personnel would be in a state of recurrent emotional crisis if they were notable to develop emotionally neutral ways of interpreting the majority of events they mustdeal with. When threat, suffering, mutilation and death are interpreted in a way which givesthem high personal relevance, though, strong cognitive and emotional responses trend tobe evoked. This would be the case, for example, if a person believed his own life werebeing seriously threatened, or the extreme events involved his own loved ones, his col-leagues, any other individuals to whom he developed a particularly strong commitment, oreven people (especially children) who were reminiscent of his loved ones.

Another important personal factor mediating the impact of an extreme event will be theprescriptive evaluations that a person makes of his own or others’ behaviour in connectionwith the event, which in turn will be based upon his personal moral philosophies.

When an extreme event is traumatic for a person, it has been observed that there are quiteoften some common features to the ensuing pattern of reactions, most notably if the per-son fails to show significant adjustments within a period of about a month. This seems tobe the case regardless of the particular type of the event that has been experienced.

Prior to 1980, the dominant tradition had been to describe these adjustment problems instressor-specific terms, for example, “rape trauma syndrome” or “post-Vietnam syndrome”.This began to change when the third edition of the American Psychiatric Association’sDiagnostic and Statistical Manual of Mental Disorders (DSM-III) included the stressor-generic diagnostic category of post-traumatic stress disorder (PTSD).

The diagnostic criteria for PTSD are given in Table 36. The month-duration criterion is par-ticularly important, as it reminds us that it is not so much the presence of such post-trau-matic stress reactions that should be a cause for concern, as their persistence for morethan a month. It is quite “normal” to be markedly distressed after experiencing a traumaticevent; significant longer-term problems become likely, however, if some definite stepstowards adjustment have not taken place during the first few weeks. As time passes, a per-son tends to become excessively concerned with disabilities stemming from the trauma,and increasingly disillusioned with any treatment that is being offered. Reliance on psy-choactive medication (quite often coupled with greater alcohol consumption) impedesrecovery, and if medical assessments and litigation processes proceed unfavourably theperson can become very retributive and resentful. Slowly but surely a person can undergowhat seems like a complete personality change: from being employed, physically fit andactive, good natured, fun-loving and self-sufficient, he or she can be unemployable, unfitand sedentary, short-tempered, depressed and dependent.

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12.2.2 Managing psychological problemsSince a proportion of professional helpers are likely to be adversely affected by traumaticaspects of their disaster work, how should such problems be managed?

One of the most important things to remember at the outset of any management planningis that each professional group has its own culture and conventions, and its own interpre-tation of reactions to potentially traumatic events. Despite disclaimers to the contrary, forexample, such reactions may actually be regarded as a deficiency or sign of weakness ina person, with serious implications for his career prospects should they ever be discov-ered. Further, most professional helpers will have been trained to be independent and self-reliant, and so even when one of them knows he has a problem, he will find it very difficultindeed to face up to the potentially humiliating fact, that perhaps for the first time in his life,something is happening which he cannot manage on its own. Anyone assisting with poten-tial problems in such groups must therefore be prepared to tread carefully, and design andpresent interventions which are not only satisfactory from a technical point of view, butwhich also “fit” the client organization.

Given this general approach, in most cases it will be possible to engage in a certainamount of anticipatory management of potential problems, by providing some low-keyawareness training. Since most groups of professional helpers already encounter poten-tially traumatic events in the course of their work in non-disaster situations, such trainingcan usually be seen to have relevance, even if local disaster is difficult to foresee. Thetraining should:

D illustrate, with the help of case studies, how it is possible for a perfectly strong,mature, professional person to be “caught-out” by an extreme experience

D show what the normal course of adjustment might entail, for problems with vary-ing degrees of severity

D explain the routine screening procedures that might be followed by their organi-sation

D describe the confidential counselling support that would be on offer should theywant to avail themselves of it

During and immediately after disaster work, sensitive management and additional personalsupport for staff will probably be the most critical factors. Disaster workers will typically bereluctant to take appropriate rest breaks, and if left to their own devices may work beyondthe point where their judgment becomes impaired. They may be unwilling to leave the sceneat the end of their duties, and may have great desire to share their experiences amongthemselves and with other workers. Others may become overwhelmed as they remove theiruniforms and begin to relate to recent events from a perspective outside of their professionalrole, or have difficulties as they contemplate returning home and being unable to talk aboutthe distressing aspects of their work. The requirement for post-incident, ad hoc debriefings,which are not so much an operational matter as having to do with satisfying personal needs,should be anticipated, and supervisors should be ready to provide them.

In the first few weeks after disaster, psychological screening or check-ups may either beprovided routinely for personnel who were centrally involved in the disaster work, or uponrequest. The credibility and acceptability of any professional psychologists who areinvolved in this should ideally have been established at the contingency planning stage,along with arrangements that ensure sufficient confidentiality to permit confident use of thefacilities by those who might need them. All practical arrangement should be planned withgreat sensitivity. If it is ever implied, for example, that all staff that have been involved inan extreme incident will necessarily experience adjustment problems (which is manifestlyuntrue), any attempt to manage the problem will be met with justifiable derision.

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For those individuals who have been adversely affected by their experiences, one or moresubsequent counselling sessions can be provided, and their general progress monitoredover a longer period. As a first step, it will usually be helpful to the person if he can talkthrough his experiences in some detail. On the one hand this will begin too help him devel-op a manageable account of the experiences (which he might than be able to share with

Table 36 Diagnostic criteria for post-traumatic stress disorder/Original source: The American Psychiatric Association/

A.

B.

C.

D.

E.

The person has experienced an event that is outside the range of usual human experienceand that would be markedly distressing to almost anyone, e.g. serious threat to one's lifeor physical integrity; serious threat or harm to one's children, spouse, or other close rela-tives and friends; sudden destruction of one's home or community; or seeing another per-son who has recently been, or is being, seriously injured or killed as a result of an accidentor physical violence.

The traumatic event is persistently re-experienced in at last one of the following ways:

1. Recurrent and intrusive distressing recollections of the event (in young children,repetitive play in which themes or aspects of trauma are expressed)

2. Recurrent distressing dreams of the event

3. Sudden acting or feelings as if the traumatic event were recurring (includes a senseof reliving the experience, illusions, hallucinations, and dissociative [flashback]episodes, even those that occur upon awakening or when intoxicated)

4. Intense psychological distress at exposure to events that symbolize or resemble anaspect of the traumatic event, including anniversaries of the trauma

Persistent avoidance of stimuli associated with the trauma or numbing of general respon-siveness (not present before the trauma), as indicated by at least three of the following:

1. Efforts to avoid thoughts or feelings associated with the trauma

2. Efforts to avoid activities or situations that arouse recollections of the trauma

3. Inability to recall an important aspect of the trauma (psychogenic amnesia)

4. Markedly diminished interest in significant activities (in young children, loss of recent-ly acquired developmental skills, such as toilet training or language skills)

5. Feeling of detachment or estrangement from others

6. Restricted range of effect, e.g. unable to have loving feelings

7. Sense of foreshortened future, e.g. does not expect to have a career, marriage, orchildren, or a long life

Persistent symptoms of increased arousal (not present before the trauma), as indicated byat least two of the following:

1. Difficulty falling or staying asleep

2. Irritability or outbursts of anger

3. Difficulty concentrating

4. Hypervigilance

5. Exaggerated startle response

6. Physiologic reactivity upon exposure to events that symbolise or resemble an aspectof the traumatic event (e.g. a woman who was raped in an elevator breaks out in asweat when entering an elevator)

Duration of the disturbance (symptoms in B, C and D) of at least a month

Specify delayed onset if onset of symptoms was at least six months after trauma

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his family), and on the other it will alert the psychologist to any potentially dysfunctionalinterpretations that could be forming. This will also be the point for some careful explana-tion of what the person is already experiencing, and what he can expect to experience overthe coming weeks.

Finally, over the next four to six weeks, it makes sense briefly to check on how a person isprogressing. If the symptoms begin to subside, this will usually indicate that adjustment isproceeding satisfactorily, but if they do not, than the time may have come for more spe-cialised counselling. In this authors’ experience, if adjustment is blocked, than there is usu-ally a perfectly understandable psychological basis for that state of affairs which, if the per-son wishes to cooperate, can be changed. One thing which is noticeable, however, is thatcertain post-traumatic adjustment problems seem to be exacerbated by non-directive coun-selling. When a person’s way of interpreting and evaluating the traumatic events amounts tobuilding a psychological trap, and is thus pathogenic, merely aiming to clarify and under-stand, can result to reinforcing the structure of the trap when really it should be dismantled.

Bibliography and reference documentsRoberts, E., “Our Quaking Earth”, Little, Brown and Company, Boston – Toronto, 1963.

Bolt, B. A., W. L. Horn, G. A. Macdonald and R. F. Scott, “Geological Hazards”, Springler-Verlag, Berlin –Heidelberg – New York, 1975.

Pan American Health Organisation (PAHO), “Emergency Health Management after Natural Disasters”,Scientific Publication No. 407, 1981.

Asian Development Bank, “Disaster Mitigation in Asia and Pacific”, 1990.

Carter W. N., “Disaster Management: A Disaster Manager’s Handbook”, Asian Development Bank, 1991.

UNDRO, “Mitigating Natural Disasters - Phenomena, Effects and Options: A manual for Policy Makers andPlanners”, New York, 1991.

Tidemann, H., “Earthquakes and Volcanic Eruptions – A handbook on Risk Assessment”, Swiss ReinsuranceCompany, Zurich, 1992.

Coburn A. and R. Spence, “Earthquake Protection”, John Wiley & Sons, Chichester, West Sussex, England,1992.

International Civil Defence Organisation (ICDO), “Rescue Manual – Elementary Techniques of Rescue”, 1993.

International Federation of Red Cross and Red Crescent Societies (IFRC), “Disaster Needs AssessmentManual”, 1993.

Alexander D., “Natural Disasters”, Chapman & Hall, New York, 1993.

WMO/UNESCO, “World Conference for Natural Disaster Reduction”, 1994.

World Health Organisation, “Planning for Emergencies, Part 2: Concepts and Definitions for EmergencyManagement in Health Sector”, 1995.

Key, D., (editor), “Structures to Withstand Disasters”, Institute of Civil Engineers, Tomas Telford Publications,London, United Kingdom, 1995.

“Megacities – Reducing Vulnerability to Natural Disasters”, Institute of Civil Engineers, Tomas TelfordPublications, London, United Kingdom, 1995.

Smith, K., “Environmental Hazards - Assessing Risk and Reducing Disaster”, 1996.

Vorobiev, Y. I, N. I. Loktionov, M. I. Faleyev, M. A. Shakhramanyan, F. K. Shoygu, V. P. Sholokh, “Disasters andMan – Book 1: The Russian Experience of Emergency Response”, Moscow, 1997.

Chapter 12.2 is arranged by extensive use of extracts from the following reference: Duckworth D. H., “DisasterWork and Psychological Trauma”, Disasters Management, Vol.1 No. 2, 1998; Dr. Duckworth is a CharteredOccupational Psychologist, and a lecturer in the Department of Management Studies and Psychology at theUniversity of Leeds, UK.

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“Floods, Causes, Effects and Risk Assessment”, A PartnerRe Group Publication, 1997.

“Third United Nations Conference on the Exploration and Peaceful Uses of Outer Space - UNISPACE III:Disaster Prediction, Warning and Mitigation”, 1998.

Duckworth D. H., “Disaster Work and Psychological Trauma”, Disasters Management, Vol.1 No. 2, 1998.

Scanlon J., “Planning for Peace and War Emergencies – learning from 70 Years of Disaster Research”,Disasters Management, Vol.1 No. 2, 1998.

The Marmara, Turkey Earthquake of August 17, 1999 - Reconnaissance Report, Technical Report MCEER-00-0001, March 23, 2000.

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BLOCK 4 - coe.int · complexes. While these advances assured significant reduction in expansion of urban areas, if not compliant with the seismic environment, in a case of major seismic