1. BABY JANE T. PUNONGBAYANBABY JANE T. PUNONGBAYAN
Seismological Observation and Earthquake Prediction DivisionSeismological Observation and Earthquake Prediction Division
Philippine Institute of Volcanology and SeismologyPhilippine Institute of Volcanology and Seismology
PHIVOLCSPHIVOLCS -- DOSTDOST
UNDERSTANDINGUNDERSTANDING
EARTHQUAKES ANDEARTHQUAKES AND
EARTHQUAKE HAZARDSEARTHQUAKE HAZARDS
2. 30 unmanned stations:30 unmanned stations:
1 in1 in OrmocOrmoc
1 in1 in MaasinMaasin
29 manned stations29 manned stations
1 in Palo1 in Palo
55 seismoseismo--volcanologicalvolcanological
observatoriesobservatories
Metro ManilaMetro Manila
micronetworkmicronetwork with 5with 5
telemeteredtelemetered
seismic stationsseismic stations
TemporaryTemporary
HinunanganHinunangan NetworkNetwork
5 stations5 stations
Network of Earthquake
Monitoring Stations in
the Philippines
5. 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 areasIntensities of affected areas
Tsunami bulletins and warningsTsunami bulletins and warnings
Advisory in times of necessaryAdvisory in times of necessary
evacuationevacuation
Information transmitted by tri-media (tv,
radio and print)
6. What have we learned?What have we learned?
PHIVOLCS is the agency mandated toPHIVOLCS is the agency mandated to
monitor earthquakes in the Philippinesmonitor earthquakes in the Philippines
A seismically active area may produceA seismically active area may produce
hundreds to thousands of earthquakes in ahundreds to thousands of earthquakes in a
brief span of time (hours to several weeks)brief span of time (hours to several weeks)
11. FaultFault
-- form in rocks when the stresses overcome theform in rocks when the stresses overcome the
internal strength of the rock resulting in a fractureinternal strength of the rock resulting in a fracture
12. THE CRUST IS FRAGMENTED
Tectonic plates
Earthquakes are found along plate boundaries
13. What have we learned?What have we learned?
Earthquakes are natural phenomenaEarthquakes are natural phenomena
brought about by slow but powerful motionsbrought about by slow but powerful motions
within the earthwithin the earth
The internal motion within the EarthThe internal motion within the Earth
induces deformation along the fragileinduces deformation along the fragile
surface of the planetsurface of the planet
Sudden ground deformation producesSudden ground deformation produces
seismic waves or earthquakesseismic waves or earthquakes
14. A weak to violent shakingA weak to violent shaking
of the ground produced byof the ground produced by
the sudden movement ofthe sudden movement of
rock materials below therock materials below the
earth’s surface.earth’s surface.
15. 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
16. 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)
17. SeismogramSeismogram
Distance of point of observation from earthquake source is determined using
the arrival times of different seismic waves, usually P and S waves
18. Locating the Epicenter
Travel Time and earth structureTravel Time and earth structure
Velocity ModelsVelocity Models
Refracted and Reflected PhasesRefracted and Reflected Phases
20. • 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 !
21. 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)
23. 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
24. MagnitudeMagnitude <energy><energy>
Compares logarithmic of amplitude withCompares logarithmic of amplitude with
distance from epicenterdistance from epicenter
Types depending on instrumentation:Types depending on instrumentation:
Period (s)Period (s)DescriptionDescriptionNameName
MomentMoment
MagnitudeMagnitude
SurfaceSurface
MagnitudeMagnitude
BodyBody
MagnitudeMagnitude
LocalLocal
MagnitudeMagnitude
MwMw
MsMs
MbMb
MlMl
> 200> 200
2020
1.01.0 –– 5.05.0
0.10.1 –– 1.01.0
WoodWood--
Anderson typeAnderson type
seismographseismograph
25. 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
26. • 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)
27. 1960 Chile earthquake (strongest1960 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 grenade
5.6 kg (12.4
lb)
0.5
Example
Approximate TNT for
Seismic Energy Yield
Richter Approximate
Magnitude (Ml)00
31. 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 toAn 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 theLarge magnitude earthquakes have occurred in the
Philippines in the pastPhilippines in the past
Large magnitude earthquakes are inevitable in the PhilippinesLarge 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 andBasic seismology deciphers information about the earth and
its movements using the imprint of the passing of seismicits movements using the imprint of the passing of seismic
waveswaves
32. Basic TermsBasic Terms
SeismologySeismology -- sciencescience
SeismicSeismic -- pertaining to earthquakepertaining to earthquake
SeismographSeismograph -- instrumentinstrument
SeismogramSeismogram –– record of earthquakerecord of earthquake
AftershockAftershock -- following thefollowing the mainshockmainshock
ForeshockForeshock ––before abefore a mainshockmainshock
33. 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.
40. 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
48. Active Fault: trace certain
Active Fault: trace approximate
Offset stream
Legend:
Faulted outcrop (Brgy. Salog, Leyte)
Salog Elementary School, Leyte
49. 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
50. Liquefaction in Hinunangan, Southern Leyte July 19, 2007
Photo courtesy of PHIVOLCS
HINUNANGAN JULY 2007 QRT Team
Brgy. Badiangon
Brgy. Das-ay
51. Liquefaction:Liquefaction: The ground loses strength and structuresThe ground loses strength and structures
built on top of it may sink and tilt...built on top of it may sink and tilt...
52. 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 areasstronger shaking in areas
near the earthquakenear the earthquake--generating faultgenerating fault
Water saturation of materials:Water saturation of materials: wet slopeswet slopes
easier to landslideeasier to landslide
READY MAPPING 2007: Dr. Arturo Daag and Ms. Angela Montes
59. COMMON QUESTIONS:COMMON QUESTIONS:
Can earthquakes be predicted?Can earthquakes be predicted?
Is there a fault passing through yourIs there a fault passing through your
school?school?
Where is theWhere is the MarikinaMarikina Fault?Fault?
Is there a risk of tsunami inIs there a risk of tsunami in
MetroManilaMetroManila??
Who are at risk?Who are at risk?
62. WVFWVF
Maximum 4mMaximum 4m
average 2maverage 2m
alongsidealongside
Manila BayManila Bay
Will notWill not
occuroccur
TsunamiTsunami
SeismicSeismic
IntensityIntensity
(PEIS)(PEIS)
FaultFault
MechanismMechanism
MagnitudeMagnitude
ModelModel
Almost VIII,Almost VIII,
IX alongsideIX alongside
MarikinaMarikina
River andRiver and
Manila BayManila Bay
Inland FaultInland Fault
7.27.2
ModelModel 0808
VIII at West ofVIII at West of
MetropolitanMetropolitan
Mania, VII atMania, VII at
other areaother area
SubductionSubduction
7.97.9
ModelModel 1313
Is there a possibility of a big earthquake inIs there a possibility of a big earthquake in MetroManilaMetroManila??
TheThe MetroManilaMetroManila Earthquake Impact Reduction Study (MMEIRS)Earthquake Impact Reduction Study (MMEIRS)
Some Earthquake Models/Scenario for Metro ManilaSome Earthquake Models/Scenario for Metro Manila
64. PEIS Intensity VIIIPEIS 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 groundConcrete 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 andLandslides and rockfallsrockfalls; Boulders thrown out near epicenter; Boulders thrown out near epicenter
Fissures or rupture observedFissures or rupture observed
Water splashes over dikes orWater splashes over dikes or oror riverbanksriverbanks
65.
66. 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.
67. ESTIMATED IMPACTS OF WORST CASE SCENARIO EARTHQUAKEESTIMATED IMPACTS OF WORST CASE SCENARIO EARTHQUAKE
(Magnitude=7.2 West Valley Fault)(Magnitude=7.2 West Valley Fault)
13%13%
170,000170,000
heavily damagedheavily damaged
or collapsedor collapsed
Residential buildingsResidential buildings
25.6% or25.6% or
350,000350,000
moderatelymoderately
damageddamaged
34,000,34,000,
90% from pressure of90% from pressure of
collapsed buildingcollapsed building
deaddeadHuman LossHuman Loss
With population of 9,932,560With population of 9,932,560
120,000120,000injuredinjured
2020 –– 25 %25 %Partly DamagedPartly Damaged
88 -- 10 %10 %Heavily DamagedHeavily DamagedPublic Purpose Buildings:Public Purpose Buildings:
Schools 1412, Hospitals 177, FireSchools 1412, Hospitals 177, Fire
Fighting 124, Police 43, MMDCCFighting 124, Police 43, MMDCC
Organizations and 17 LGU CityOrganizations and 17 LGU City
and Municipal Halls 53and Municipal Halls 53
Four out of ten buildings and houses will be damaged
68. PHIVOLCS has the knowledge, it is ourPHIVOLCS has the knowledge, it is our
mission to prepare the public.mission to prepare the public.
Some of our information andSome 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
