JOAN CRUZ SALCEDOPHILIPPINE INSTITUTE OF VOLCANOLOGY AND SEISMOLOGY –

DEPARTMENT OF SCIENCE AND TECHNOLOGYPHIVOLCS-DOST

Earthquakeand

TsunamiTraining on Disaster Risk Reduction: The Role of DOST Regional Offices

PHIVOLCS Auditorium, Quezon City11 December 2013

Number of Earthquakes 1897 – 2011Magnitude 5 and above

No. of earthquakes

No. of earthquakesthat caused damages

Magnitude

1.87%

6.67%

59.68%100%

Data Source: PIVS

Some Historical Churches in the Philippineswith earthquake accounts

“partially destroyed by earthquake, 1600”“destroyed by the earthquake of 1645”

“destroyed by the earthquake of 3 June 1863” 1645

1863

“withstood the earthquakes of 1645,1658, 1754, and 1863”

“the masonry roof of the Churchcollapsed in the earthquakes of 1880”

Some Historical Churches in the Philippineswith earthquake accounts

Some Significant Earthquakes1968 August 2 M 7.3

The Sunday Times, 1968 August 4

1968

A weak to violent shakingof the ground produced bythe sudden movement ofrock materials below theearth’s surface.

MAGNITUDE measures theenergy released at thesource of the earthquake

INTENSITY measures the strength ofshaking produced by the earthquake ata certain location

Volcanic- earthquakes producedby movement of magmabeneath volcanoes

Tectonic- earthquakes produced by

sudden movement along faultsand plate boundaries

Magma

Types of Natural Earthquakes

Tectonic Plates

Distribution of earthquakeepicenters worldwide

EQUATOR

Tectonic Setting of thePhilippine Archipelago

Types of Plate Boundaries

TRANSFORM DIVERGENT CONVERGENT

Faults-breaks or zones of weakness in rocks along whichdisplacements had occurred or can occur again.They may extend hundreds of kilometers across theearth’s surface and tens of kilometers downward

BEFOREFAULTING

REVERSE

NORMAL FAULT

STRIKE-SLIP

Types of Fault Movement

Seismicity of the Philippines

~ an average of 20earthquakes recorded

per day

~100-150 feltearthquakes

per year

~90 destructiveearthquakes for the past

400 years

Earthquake Hazards

• Ground Rupture

• Ground Shaking

• Liquefaction

• Landslide

• Tsunami

A dangerousphenomenon,substance, humanactivity or condition thatmay cause loss of life,injury or other healthimpacts, propertydamage, loss oflivelihoods and services,social and economicdisruption, orenvironmental damage.

Drawing after Harris (1994)

Ground shakingthe disruptive up and down and sideways motion

experienced during an earthquake

1990 Luzon Earthquake 1995 Kobe Earthquake

• Magnitude: we feel more intense shaking from a bigearthquake than from a small one.

factors that primarily determinewhat you feel in an earthquake

a big earthquake!

a small one.

than from

• Distance from the fault: earthquake waves die off asthey travel through the earth so the shaking becomes lessintense farther from the fault.

Epicentral Distance

factors that primarily determinewhat you feel in an earthquake

• Local Soil Conditions: A soft, loose soil will shake moreintensely than hard rock at the same distance from the same earthquake.

factors that primarily determinewhat you feel in an earthquake

“How earthquake moves?”

Kobe, Japan, 1995

Baclayon Church, Bohol

September 2013 October 2013KV KV

Dauis Church, Bohol

September 2013 October 2013KV KV

Fault (Ground)rupture

creation of new or therenewed movements ofold fractures, oftentimeswith the two blocks onboth sides moving inopposite directions

Groundrupture

2013 Bohol Earthquake Magnitude : 7.2Ground Rupture

MITIGATION MEASURE:No construction of houses,schools and critical facilities

on top of an active fault; bufferzone of at least 5 meters away

from the fault trace

Death and injuries from surface faulting arevery unlikely, but casualties can occurindirectly through fault damage to structures

• houses

• commercial buildings

• railroads

• highways

• bridges

• water lines

• gas lines

http://www.phivolcs.dost.gov.ph

Liquefaction

Subsidence

Rise of buried pipes, tanks

Lateral spreading

a process that transforms the behaviorof a body of sediment from that of a

solid to that of a liquid

Landslides and rockfallsslope failures in steep or hilly slopes

Landslide causes

Three types of causes of landslides thatcause most of the damaging landslidesaround the world:

• Landslide and Water

• Landslide and Seismic Activity

• Landslide and Volcanic Activity

Landslides and Seismic Activity (Earthquake)Ground shaking, shaking-caused dilation of soil materials, whichallows rapid infiltration of water.

A series of wavesgenerated by variousgeological processes

Japanese termmeaning “harborwaves” or “alon sapantalan”

Generally byEARTHQUAKES

Less commonly by Sub-aerial to Submarine

LANDSLIDES

Infrequently byVOLCANIC

ERUPTIONS

Very rarely byMETEORITE IMPACTS

NHK, Japan Tsunami, 11 march 2011

Stages of Tsunami

Inundation

Propagation

Generation

Tsunami Generation

www.tsunami.noaa.gov

Tsunami Generation

Tsunamis are generated primarily by tectonicdislocations under the sea, which are caused by shallowfocus earthquakes along areas of subduction.

The upthrusted and downthrusted crustal blocksimpart potential energy into the overlying water mass withdrastic changes in the sea level over the affected region.

The energy imparted into the water mass results intsunami generation.

Earthquake and Tsunami Generation along Trenches

To generate a tsunami•the fault where the earthquakeoccurs must be underneath or nearthe ocean

•Cause vertical movement of theseafloor (up to several meters)

•over a large area (up to hundredthousand sqkm)

•shallow focus earthquakes (depthless than 70km)

Earthquakes & Tsunamis

Not all earthquakes generate tsunami

Bathymetry: the science ofmeasuring depths of the ocean,lakes, seas, etc.

Topography: the shape ofthe land

Landcover: roughness

Propagation & Inundation

WAVEHEIGHT

INUNDATIONArea flooded with water bythe tsunami

How Fast?

Over 800 kilometers perhour (kph) in deep oceanover 6000m deep

30 to 50 kph nearshorelines

Tsunami speed dependson the depth of water

waveheight

inundation

How Big?

Offshore andcoastal featurescan determine thesize and impact oftsunami waves.

Landcover/Surface Roughness

• Grassland

• Areas coveredwith buildings

• Areas denselycovered withforest

Tsunamis that strike coastal locations are almost alwayscaused by earthquakes. These earthquakes might occurfar away or near where you live. While earthquakesoccur in all ocean basins around the world, most do notgenerate tsunamis

Tsunami Facts

Some tsunamis can be very large, and they causeimpacts like flashfloods. Later waves are often full ofdebris.

2004 Tsunami,Indonesia

Tsunami Facts

Run-up height could be as high as 10 meters or more

Tsunami Facts

4 storeys x ~3 meters/storey = ~12 meters

2011 Japan Tsunami

All low lying coastal areas can be struck by tsunamis

Tsunami Facts

1976 Moro Gulf Tsunami

Tsunami FactsA tsunami consists of series of waves. The first wavemay not be the largest. The danger from a tsunami canlast for several hours after the arrival of the first wave.Tsunami waves typically do not curl and break, so do nottry to surf a tsunami!

Tsunami Accounts: The 1976 Moro GulfTsunami

Descriptions:

3 or 4 waves (one person said 9) ==there was more than 1 wave

1 to 5 minutes interval

maximum inundation = 2 km

maximum water recession (with suckingsound) = 2 km

Tsunami simulation, source Manila Trench

Sometimes a tsunami initially causes the water near theshore to recede, exposing the ocean floor.

Tsunami Facts

Tsunami FactsThe force of some tsunami is very strong. Large rocks,boats and other debris can be moved inland and can killand injure people.

Transported bancas (Sakol, Island), 1976 Moro Gulf Tsunami

1964 Alaska Earthquake

2011 Japan Earthquake

Tsunamis can travel up rivers that lead to the sea.

Tsunami Facts

Japan (almost 5 months after the Tsunami)

Tsunami Impacts

Photos by RUSolidum, PHIVOLCS

Kesennuma

Ogatsu

• Movement of heavy objectsand impact to structures

Ship on the house: 2004 Sumatra Earthquake Tsunami

Ship on the house: 2011 Tohoku Earthquake Tsunami

© DigitalGlobe

Tsunami Impacts

Banda Aceh, Indonesia,before & after the 26 Dec2004 Northern Sumatra

Tsunami

» Coastal & inlandflooding & erosion

Tsunami Impacts

Miyako

• Flooding of coastalareas

• Drowning of people• Damage to properties

Natori

From AP

From Kyodo News

Rikuzentakata

PHIVOLCS

» Sea water is murky& may cause healthcomplications wheningested.

» Water in wellsbecome salty & notpotable

» Agricultural landsare rendereduseless for someyears.

Tsunami Impacts

60

The Philippines and The Tsunami Threat

Tsunami sources (image from ComMIT)

Tsunami Prone Areas Locations of earthquake thatgenerated destructive tsunami

Types of TsunamiType Source Lead time

earthquake totsunami

Warning mechanism inplace

LOCAL trench or faultin Philippineregion, usuallyless than 200km fromshoreline

2 – 60minutes

Community-based

must rely on natural signs suchas moderate to intenseshaking in coastal area,unusual water level rise or fall,and unusual sound

DISTANTRegionalor Trans-Pacific

trench or faultoutside thePhilippineregion(ex. Japan,Hawaii, Chile)

1 – 24hours

International CentersPacific Tsunami WarningCenter, NW Pacific TsunamiAdvisory Center

PHIVOLCSOCD

Tsunami simulation of 1700 Cascadia Earthquake

Distant Tsunami

Local Tsunami

1976 Moro Gulf Tsunami

1992 Eastern Mindanao Tsunami

1994 Mindoro Tsunami

Felt earthquake

Unusual &sudden rise or fallof coastal waters

Exposure of corals,underwater rocks, andmarine life

Unusual Sound

D R O P

Natural Signs of an Impending Local Tsunami

- Located inside the ChineseCemetery

The Ruby Tower Memorial1968 August 2 M7.3

References:PHIVOLCS Info materialswww.phivolcs.dost.gov.ph

UNESCO-IOC. Tsunami, The Great Waves.IOC Brochure 2006-2. Paris, UNESCO, 2006Some images downloaded from the internet

Thank you for your attention…

PHIVOLCS-DOSTPHIVOLCS Bldg., CP Garcia Avenue, UP Campus

Diliman, Quezon CityT 426 1468 to 79

www.phivolcs.dost.gov.ph

JlCruz-Salcedo