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