earthquake and its hazards

BABY JANE T. PUNONGBAYANBABY JANE T. PUNONGBAYANSeismological Observation and Earthquake Prediction DivisionSeismological Observation and Earthquake Prediction Division

Philippine Institute of Volcanology and SeismologyPhilippine Institute of Volcanology and SeismologyPHIVOLCS PHIVOLCS -- DOSTDOST

UNDERSTANDING UNDERSTANDING

EARTHQUAKES AND EARTHQUAKES AND

EARTHQUAKE HAZARDSEARTHQUAKE HAZARDS

�� 30 unmanned stations: 30 unmanned stations: 1 in 1 in OrmocOrmoc

1 in 1 in MaasinMaasin

�� 29 manned stations29 manned stations

1 in Palo1 in Palo

�� 5 5 seismoseismo--volcanologicalvolcanologicalobservatoriesobservatories

�� Metro Manila Metro Manila micronetworkmicronetwork with 5 with 5 telemeteredtelemetered

seismic stationsseismic stations

�� Temporary Temporary HinunanganHinunangan NetworkNetwork

5 stations5 stations

Network of Earthquake Monitoring Stations in

the Philippines

Seismic monitoring station in El Nido, Palawan

PHIVOLCS seismologists: PHIVOLCS seismologists: earthquake huntersearthquake hunters

4,000th quake in 4 days!

PHIVOLCS: Source of earthquake information in the PhilippinesPHIVOLCS: Source of earthquake information in the Philippines

�� Details of earthquake location: Details of earthquake location:

�� Origin time, coordinates, depth, Origin time, coordinates, depth,

source (tectonic or volcanic), source (tectonic or volcanic),

generatorgenerator

�� Intensities of affected areas Intensities of affected areas

�� Tsunami bulletins and warningsTsunami bulletins and warnings

�� Advisory in times of necessary Advisory in times of necessary

evacuationevacuation

Information transmitted by tri-media (tv,

radio and print)

What have we learned?What have we learned?

�� PHIVOLCS is the agency mandated to PHIVOLCS is the agency mandated to

monitor earthquakes in the Philippinesmonitor earthquakes in the Philippines

�� A seismically active area may produce A seismically active area may produce

hundreds to thousands of earthquakes in a hundreds to thousands of earthquakes in a

brief span of time (hours to several weeks)brief span of time (hours to several weeks)

EarthEarth

Our planet is dynamic

The outermost layer is broken into pieces

These pieces called “plates” are moving, away or toward each other

Mantle convection is driving the earth’s tectonic platesMantle convection is driving the earth’s tectonic plates

The Earth is dynamic: Plate TectonicsThe Earth is dynamic: Plate Tectonics

The Philippines is a region between tectonic plates

EQUATOR

FaultFault

-- form in rocks when the stresses overcome the form in rocks when the stresses overcome the internal strength of the rock resulting in a fracture internal strength of the rock resulting in a fracture

THE CRUST IS FRAGMENTED

�Tectonic plates

Earthquakes are found along plate boundaries

What have we learned?What have we learned?

�� Earthquakes are natural phenomena Earthquakes are natural phenomena brought about by slow but powerful motions brought about by slow but powerful motions within the earthwithin the earth

�� The internal motion within the Earth The internal motion within the Earth induces deformation along the fragile induces deformation along the fragile surface of the planetsurface of the planet

�� Sudden ground deformation produces Sudden ground deformation produces seismic waves or earthquakesseismic waves or earthquakes

A weak to violent shaking A weak to violent shaking

of the ground produced by of the ground produced by

the sudden movement of the sudden movement of

rock materials below the rock materials below the

earth’s surface.earth’s surface.

2. Volcanic- earthquakes produced

by movement of magma beneath volcanoes

1. Tectonic- earthquakes produced

by sudden movement along faults and plate boundaries

TYPES OF NATURAL EARTHQUAKESTYPES OF NATURAL EARTHQUAKESTYPES OF NATURAL EARTHQUAKESTYPES OF NATURAL EARTHQUAKES

Particle Motion upon

passage of different

types of seismic waves

P – primary wave;

displacement of media along

direction of propagation

(up-down)

S – secondary;

displacement of media

perpendicular to direction of

wave propagation (sideways)

Surface waves:

1. Love waves

2. Rayleigh waves (rotational)

SeismogramSeismogram

Distance of point of observation from earthquake source is determined using

the arrival times of different seismic waves, usually P and S waves

Locating the Epicenter

�� Travel Time and earth structure Travel Time and earth structure

�� Velocity ModelsVelocity Models

�� Refracted and Reflected PhasesRefracted and Reflected Phases

FAULT

FOCUS vs. EPICENTERFOCUS vs. EPICENTER

• at least 20 earthquakes are recorded per day

• 4 – 5 earthquakes are felt per week

Instrumental Data (ISC) 1964-1999

Philippines is an earthquake country !

M7.5 01 Apr 1955 Lanao(291/713)

M7.3 02 Aug 1968 Casiguran(270/600)

M7.3 07 Apr 1970 Baler (15/200)

17 Aug 1976 Moro Gulf (3,739/8,000)

16 July 1990 Luzon (1,283/2,786)

15 November 1994 Mindoro(78)

Fact:

The Philippine Archipelago

has a complex tectonic setting

with several trenches and

many active faults

perceived strength of an earthquake based on relative effect to people and structures; generally higher near the epicenter

based on instrumentally

derived information and

correlates strength with the amount of total energy

released at the earthquake’s

point of origin

Two ways of describing the strength of an earthquakeTwo ways of describing the strength of an earthquakeTwo ways of describing the strength of an earthquakeTwo ways of describing the strength of an earthquake

1. . . . Intensity 2. 2. 2. 2. Magnitude

Magnitude Magnitude <energy><energy>

�� Compares logarithmic of amplitude with Compares logarithmic of amplitude with distance from epicenterdistance from epicenter

�� Types depending on instrumentation:Types depending on instrumentation:

Period (s)Period (s)DescriptionDescriptionNameName

Moment Moment

MagnitudeMagnitude

Surface Surface

MagnitudeMagnitude

Body Body

MagnitudeMagnitude

Local Local

MagnitudeMagnitude

MwMw

MsMs

MbMb

MlMl

> 200> 200

2020

1.0 1.0 –– 5.05.0

0.1 0.1 –– 1.01.0

WoodWood--

Anderson type Anderson type

seismographseismograph

RICHTER MAGNITUDE SCALERICHTER MAGNITUDE SCALE

Earthquakes with M over 9 have never occurred since the data based on the

seismographic observations became available.1010

M over 9 have never occurred since the data based on the seismographic observations

became available.99

M 8 to 9 are the "great earthquakes" occurring once or twice a year. When in land areas,

damages affect wide areas. When under the sea, considerable tsunamis are produced.

Many aftershocks occur in areas approximately 100 to 1,000 kilometers in diameter.

88

M 7 to 8 are the "major earthquakes“; can cause considerable damages near epicenters;

may generate tsunamis. 77

M 6 to 7 are "strong earthquakes“; accompanied by local damages near epicenters.66

M 5 to 6 are "earthquakes with moderate strength“; felt over the wide areas; some of

them cause small local damages near the epicenter.55

M 4 to 5 are "feeble shocks" where damages are not usually reported.44

M 3 to 4 are "very feeble shocks" and only felt near the epicenter.33

M below 3 are "hardly perceptible shocks" and are not felt. 22

magnitude below 1 are only detectable when an ultra sensitive seismometer is operated

under favorable conditions.11

• There are different types of magnitude depending on type of seismograph used: Ml, mb, Ms, Mw, Mwp, etc.

• Magnitude scale is open ended (no limit)

1960 Chile earthquake (strongest 1960 Chile earthquake (strongest

recorded earthquake)recorded earthquake)9.5

estimate for a 2 km rocky meteorite impacting at 25

km/s1 teraton10.0

Catastrophic to whole earthCatastrophic to whole earth12.0

2004 Indian Ocean earthquake32 gigatons9.3

1990 Baguio (Luzon) earthquake(67,000x hiroshima)

1 gigaton7.8

Nagasaki atomic bomb32 kiloton5.0

Small atomic bomb1 kiloton4.0

Construction site blast32 kg (70 lb)1.0

large Hand grenade5.6 kg (12.4 lb)

0.5

ExampleApproximate TNT for

Seismic Energy Yield

Richter Approximate

Magnitude (Ml)00

Indonesia 2004

INTENSITY• Decreases with distance

from source

• can be gauged by Assumption

students!! Very easy…

INTENSITY VIII

INTENSITY IX

INTENSITY VIII

INTENSITY VII

What have we learned?What have we learned?

�� Magnitude = instrumentsMagnitude = instruments

�� Intensity = personal observationsIntensity = personal observations

�� An increase of one unit on the Richter Scale corresponds to An increase of one unit on the Richter Scale corresponds to approximately a 30approximately a 30--fold increase in the total energy released. fold increase in the total energy released.

�� Large magnitude earthquakes have occurred in the Large magnitude earthquakes have occurred in the Philippines in the pastPhilippines in the past

�� Large magnitude earthquakes are inevitable in the Philippines Large magnitude earthquakes are inevitable in the Philippines because of its geodynamic setting and the presence of faultsbecause of its geodynamic setting and the presence of faults

�� YOU and your class may contribute in intensity reporting!YOU and your class may contribute in intensity reporting!

�� Basic seismology deciphers information about the earth and Basic seismology deciphers information about the earth and its movements using the imprint of the passing of seismic its movements using the imprint of the passing of seismic waveswaves

Basic TermsBasic Terms

�� Seismology Seismology -- sciencescience

�� Seismic Seismic -- pertaining to earthquakepertaining to earthquake

�� Seismograph Seismograph -- instrumentinstrument

�� Seismogram Seismogram –– record of earthquakerecord of earthquake

�� Aftershock Aftershock -- following the following the mainshockmainshock

�� Foreshock Foreshock ––before a before a mainshockmainshock

Seismic Hazards:Seismic Hazards:

dangers posed by large earthquakesdangers posed by large earthquakes

• Ground Shaking - shake

• Ground Rupture - cut

• Liquefaction - very soft soil

• Landslides - slope failure

• Tsunami - waves

Secondary Hazards:•Fire•Lateral spreading, etc.

Intense shaking, earthquake of Kobe, Japan 1995Intense shaking, earthquake of Kobe, Japan 1995

intense shaking + weak structure = building damage or collapse

Ex. Hyatt Hotel in Baguio City after the magnitude 7.8 earthquake of July 16, 1990

USA

INDIA

Ground rupture with vertical displacementGround rupture with vertical displacement

Intense shaking + loosely hanged objects = Intense shaking + loosely hanged objects =

falling objectsfalling objects

Hazard 2:Hazard 2: GROUND RUPTUREGROUND RUPTURE

�� fissuringfissuring or faulting along the surface

� The creation of new or the renewal of movements of old fractures, oftentimes with the two blocks on both sides moving in opposite directions

Groundrupture

Seismic Seismic

HazardsHazards

•• Reverse FaultReverse Fault

Photo of Nojima Fault in Japan, fissured during the M=7.2 1995 Kobe earthquake

Ground rupture and fissuringTaiwan Earthquake, 1999

Active Fault: trace certain

Active Fault: trace approximate

Offset stream

Legend:

Faulted outcrop (Brgy. Salog, Leyte)

Salog Elementary School, Leyte

Hazard 3: LiquefactionHazard 3: Liquefaction

-- a process that transforms the behavior of a body of sediment from that of a solid to that of a liquid

Liquefaction in Hinunangan, Southern Leyte July 19, 2007

Photo courtesy of PHIVOLCS HINUNANGAN JULY 2007 QRT Team

Brgy. Badiangon

Brgy. Das-ay

Liquefaction: Liquefaction: The ground loses strength and structures The ground loses strength and structures

built on top of it may sink and tilt...built on top of it may sink and tilt...

EarthquakeEarthquake--induced Landslidesinduced Landslides

��Occurrence of a strong earthquakeOccurrence of a strong earthquake

�� Elevated areas:Elevated areas: steeper slopes, more pronesteeper slopes, more prone

��Thick soil cover:Thick soil cover: more loose materials to fallmore loose materials to fall

��Proximity to fault:Proximity to fault: stronger shaking in areas stronger shaking in areas

near the earthquakenear the earthquake--generating faultgenerating fault

��Water saturation of materials:Water saturation of materials: wet slopes wet slopes

easier to landslideeasier to landslide

READY MAPPING 2007: Dr. Arturo Daag and Ms. Angela Montes

LandslideLandslide

Hazard 4:Hazard 4: Landslides and Landslides and RockfallsRockfalls

HinunanganHinunangan, Southern , Southern LeyteLeyte July 19, 2007 11:10 PM July 19, 2007 11:10 PM

Magnitude 5.5 EarthquakeMagnitude 5.5 Earthquake

Intensity VII in Hinunangan

Landslide in Brgy.

Biasong

Photo: Punongbayan, BJT 2007

Tension cracks in Tension cracks in BrgyBrgy. . ManalogManalog July 19, 2007 July 19, 2007

(Intensity VII in (Intensity VII in HinunanganHinunangan))

Ground Failure Ground Failure -- LandslideLandslideINTENSE shaking +INTENSE shaking +

�� SlopeSlope

�� VegetationVegetation

�� Water contentWater content

�� PrePre--existingexistingstructuresstructures

Secondary Hazard: FireSecondary Hazard: Fire

COMMON QUESTIONS:COMMON QUESTIONS:

��Can earthquakes be predicted? Can earthquakes be predicted?

�� Is there a fault passing through your Is there a fault passing through your school?school?

��Where is the Where is the MarikinaMarikina Fault? Fault?

�� Is there a risk of tsunami in Is there a risk of tsunami in MetroManilaMetroManila??

��Who are at risk?Who are at risk?

~3 km

WVFWVF

Maximum 4mMaximum 4m

average 2m average 2m

alongside alongside

Manila BayManila Bay

Will not Will not

occur occur

TsunamiTsunami

Seismic Seismic

Intensity Intensity

(PEIS)(PEIS)

Fault Fault

MechanismMechanism

MagnitudeMagnitude

ModelModel

Almost VIII, Almost VIII,

IX alongside IX alongside

MarikinaMarikina

River and River and

Manila BayManila Bay

Inland FaultInland Fault

7.27.2

ModelModel 0808

VIII at West of VIII at West of

Metropolitan Metropolitan

Mania, VII at Mania, VII at

other areaother area

SubductionSubduction

7.97.9

ModelModel 1313

Is there a possibility of a big earthquake in Is there a possibility of a big earthquake in MetroManilaMetroManila??The The MetroManilaMetroManila Earthquake Impact Reduction Study (MMEIRS)Earthquake Impact Reduction Study (MMEIRS)

Some Earthquake Models/Scenario for Metro ManilaSome Earthquake Models/Scenario for Metro Manila

HAZARD MAPPINGEx. Groundshaking for West Valley Fault

Mag=7.2 Scenario 08

INVENTORY OF CRITICAL FACILITIESEx. Schools

PEIS Intensity VIII PEIS Intensity VIII –– Very DestructiveVery Destructive�� People are panicky and find it difficult to stand even outdoorsPeople are panicky and find it difficult to stand even outdoors

�� Many wellMany well--built buildings are considerably damagedbuilt buildings are considerably damaged

�� Concrete dikes and foundations of bridges destroyed by ground Concrete dikes and foundations of bridges destroyed by ground settlingsettling

�� Railway tracks may be broken; tombstones may be displaced, Railway tracks may be broken; tombstones may be displaced, twisted or overturnedtwisted or overturned

�� Utility posts, towers and monuments may tilt or toppleUtility posts, towers and monuments may tilt or topple

�� Water and sewer pipes may be bent, twisted or brokenWater and sewer pipes may be bent, twisted or broken

�� Sinking or titling of structures due to liquefactionSinking or titling of structures due to liquefaction

�� Landslides and Landslides and rockfallsrockfalls; Boulders thrown out near epicenter; Boulders thrown out near epicenter

�� Fissures or rupture observedFissures or rupture observed

�� Water splashes over dikes or Water splashes over dikes or oror riverbanksriverbanks

August 2, 1968 (Ms 7.3); Casiguran

Fault-East Luzon Trench region

The Ruby Tower in Binondo,

Manila, a large six-storey

building containing 38

commercial units in its first two

floors and 76 residential units

in its upper four floors; Most of

the building collapsed except

for a part of the northern end

of its first and second floors.

268 persons died and 260 were

injured.

ESTIMATED IMPACTS OF WORST CASE SCENARIO EARTHQUAKE ESTIMATED IMPACTS OF WORST CASE SCENARIO EARTHQUAKE

(Magnitude=7.2 West Valley Fault)(Magnitude=7.2 West Valley Fault)

13%13%

170,000170,000

heavily damaged heavily damaged

or collapsedor collapsedResidential buildingsResidential buildings

25.6% or25.6% or

350,000 350,000

moderately moderately

damageddamaged

34,000, 34,000,

90% from pressure of 90% from pressure of

collapsed buildingcollapsed building

deaddeadHuman LossHuman Loss

With population of 9,932,560 With population of 9,932,560

120,000120,000injuredinjured

20 20 –– 25 %25 %Partly DamagedPartly Damaged

8 8 -- 10 %10 %Heavily DamagedHeavily DamagedPublic Purpose Buildings: Public Purpose Buildings:

Schools 1412, Hospitals 177, Fire Schools 1412, Hospitals 177, Fire

Fighting 124, Police 43, MMDCC Fighting 124, Police 43, MMDCC

Organizations and 17 LGU City Organizations and 17 LGU City

and Municipal Halls 53and Municipal Halls 53

Four out of ten buildings and houses will be damaged

PHIVOLCS has the knowledge, it is our PHIVOLCS has the knowledge, it is our

mission to prepare the public.mission to prepare the public.

Some of our information and Some of our information and

earthquake campaigns:earthquake campaigns:

�� Nationwide lectures and seminarsNationwide lectures and seminars

��Earthquake drillsEarthquake drills

�� Tsunami warning systemsTsunami warning systems

�� Tsunami warning signageTsunami warning signage

�� Tsunami drillsTsunami drills

Make the drill a nice learning experience …

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

For requests/inquiries:

Director Renato U. Solidum, Jr.PHIVOLCS Bldg., C.P. Garcia Ave.

U.P. Diliman, Q.C. 1101

Tel: 426-1468 loc. 112 or 124 or 125

Fax: 927-8366