Integration and Magnitude Homogenization of the Egyptian Earthquake Catalogue 2008
A magnitude 8 earthquake releases as much energy as...
Transcript of A magnitude 8 earthquake releases as much energy as...
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Assoc. Prof. Dr. Wan Zuhairi Wan Yaacob
Program Geologi
UKM
G E M P A B U M I
(EARTHQUAKE)
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10 largest earthquake in the world
1. Chile (9.5) -- 1960
2. Alaska (9.5) -- 1964
3. Northen Sumatera (9.1) – 26.12.2004
4. Kamchatka (9) -- 1952
5. Equador (8.8) -- 1906
6. Alaska (8.7) - 1965
7. Northern Sumatera (8.6) – 28.03.2005
8. Tibet (8.6) - 1950
9. Alaska (8.6) - 1957
10. Benda Sea Indonesia (8.5) - 1938
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Turkey Earthquake
• Magnitude 7.4
• August 17, 1999
• Killed 15,000 people
• Poor and improper
construction of
buildings (seismic
shaking)
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MIRACULOUS: A mosque is
seen still standing of the town
of Meulaboh, Aceh Province,
Indonesia. (150km dari
epicentre, 10,000 mati)
PENGAJARAN !!!!???
Sedutan dari Akbar harian:
“Satu fenomena yang menunjukkan
kekuasaan Tuhan dan binaan yang
bagus”
“Dia menghukum kita kerana
keangkuhan tetapi melindungi
rumahnya”
“Ujian dari Allah”
“saya memanjat menara masjid dan
memegang kuat wayar eletrik hingga
air surut”
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Earthquake catastrophic
Date Place Magnitude People killed
16th century
(1500s)
China 850,000
1886 South Carolina,
US
60
1906 San Francisco 700
1923 Tokyo 143,000
1976 China 650,000
1985 Mexico 10,000
1989 San Francisco 62
1993 India 6.3 7600
1994 Los Angeles 6.6 (1m
uplift!!)
61/51
1995 Kobe, Japan 5000
2004 Sumatera 9.0 250,000
Apakah penyebab perbezaan kematian di India dan LA ??
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Animas
90% of earthquakes occur at or near
plate boundaries animas
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EARTHQUAKE
The vibration of earth caused
by sudden release of
energy beneath earth’s
surface, usually as a result
of displacement of rocks
along fractures known as
faults.
Haiti earthquake
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Old ideas
• The movement of some organism
on which Earth rested.
• Japan – giant catfish
• Mongolia – giant frog
• China – an ox (large horned
animal)
• India – giant mole (burrowing
animal)
• South America – whale
• Dragon ???
• Aristotle : atmospheric winds
God is angry, or else the
plates along San Andreas
fault have slipped again
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New Ideas
• Faults (especially plate boundaries)-
Richter, 1958
• Landslides
• Volcanic Eruptions
• Filling of Reservoirs (Dams)
• Atomic Explosions
• Conspiracy theory - HAARP
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Elastic rebound theory
(teori pantulan kenyal)Slow deformation of the crust (creep) until strength of rock is exceeded.
Then, rupture occurs (earthquake).
Eg: 1. 50 years before 1906 San Francisco earthquake – offset creep 3m
2. Movement during earthquake 6m in 40 seconds !!
-Keadaan saling mengunci
-Gelinciran tertangguh lama
-Pengumpulan tenaga keterikan kenyal
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How does it
happen?
Elastic Rebound
Theory
(Teori elastik
balikan semula)
Teori pantulan
kenyal
ANIMATION
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Terminology
• EPICENTER / epipusat: location of earthquakes projected at the surface.
• HYPOCENTER or FOCUS/Foci: where earthquake actually happened. Location of the earthquake at depth. Epicenter is directly above the hypocenter.
• Main Shock: Largest and generally First earthquake in a sequence.
• Aftershock: Smaller earthquakes after first main shock. Can last as much as a month afterward. Can be almost as large as main shock, generally smaller. Decrease in magnitude with time.
• Foreshock: An earthquake that occurs prior to a large one.
Foreshocks & Aftershocks
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FORESHOCKS
-Hours/days before
-Does not always occur
MAJOR EARTHQUAKE
(main shock)
AFTERSHOCKS
-minutes to months
after major quake
animation
Fault Activity
• Fault Activity:
– active if moved during the
past 10,000 years (Holocene
Epoch);
– Potentially active (1.65 M –
10,000 years);
– Inactive (>> 1.65 M)
• Nuclear power plant
– once in 50,000 years
– >once in 500,000 years
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• 2 concepts:-
– (1) Slip rate : ratio of displacement to time interval
• Eg: 1 m displacement in time interval 1000 years;
then slip rate is 1mm per year
– (2) Recurrence interval
3 methods:-
• (i) Paleoseismic data : average time intervals between
earthquake (setiap 100 tahun?)
• (ii) Slip rate : Eg – 1 m average displacement per event;
slip rate 2 mm per year; recurrence interval = 500 years
• (iii) Seismicity: using historical earthquake & averaging the
time (sama spt (i)??)
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Fault Activity
Tectonic creep
• Rayapan tektonik
• Tectonic creep is the almost
constant movement of
certain fault blocks that
allows strain energy to be
released without causing
major earthquakes.
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Soil creep
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Pengelasan gempa berdasarkan kedalaman titik
focus
– Shallow focus (0-
70km)
– Intermediate focus (70
– 300km)
– Deep focus (300 –
700km)
(little/no damage)
-- >700km ???
More frequent
Mantle behaves plastically; deforming
continuously as ductile substances, no
storing up strain energy
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Seismic waves
• BODY WAVES (travel thru earth)
– (i) P waves or primary
– (ii) S waves or secondary
• SURFACE WAVES (travel along the
surface)
– (i) Rayleigh waves
– (ii) LOVE waves
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BODY WAVES
– (i) P waves or primary
• Fastest waves; P wave velocity = 6 km per second
• Travel thru solids;liquids;gases
• Mechanism: Push-pull/expanded-compressed
• Return to original volume
• Compressional waves (movement of particles in the
direction of wave movement), like sound waves
– (ii) S waves or secondary
• Slower than P-waves (3.6 km/sec).
• Travel thru solids only
• Shear waves (gelombang ricih)
• Move material perpendicular to the direction of travel
• Like ocean waves
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SURFACE WAVES
• Slower than body waves
• Produce a rolling and swaying motion
• Surface waves confined to the Earth’s surface like ocean waves.
• Surface waves are very destructive
• (i) Rayleigh waves– Rock particles move in vertical rolling motion (orbital).
• (ii) Love waves– Rock particles move SIDE-SIDE in a horizontal plane
– Travel faster than Rayleigh.
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Seismic waves
Body waves
Surface waves
swaying
rolling
Wave
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Comparing Earthquake
1.Calculate the energy released (Magnitude)
Quantitative measurement of energy released
2.Evaluate the impact on people and
structures (Intensity)
Qualitative assessment of the kinds of damage done
3.Ground accelerations (measure the severity
of ground shaking
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How Are Earthquake Magnitudes Measured?
• The Richter Scale– invented by Charles F. Richter &
Beno Gutenberg in 1934 (1935?) - seismologist
– is calculated from the amplitude of the largest seismic wave recorded for the earthquake
• The Mercalli Scale– Invented by Giuseppe Mercalli in
1902
– the observations of the people who experienced the earthquake to estimate its intensity
Charles Richter studying a seismogram
(From Walker, 1982)
Giuseppe Mercalli (From Walker, 1982)
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Richter magnitude, M (quantitative)
- Calculation of the amount of energy released during earthquake
–Based on seismograph
–Size of earthquake
–9.5 (largest recorded). MAX – 10; >9 improbable (mustahil kerana batuan).
– Intensity --- depends on Geology: unconsolidated sediment > hard rock
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– The scale is logarithmic
• M7 = 10x ground motion (disturbance/amplitude)
M6
• M7 = 301x energy released M6
• M8 = 900 x (=302) energy of M6
• M7 = 27,000 x (=303) energy of M4
• M2 – the smallest quake felt by humans
• M5 – potential damage
• 1906 San Francisco earthquake M8.2
• 2004 Sumatera Earth Quake M9.0
“A magnitude ZERO earthquake is about equal in energy
to a stick of dynamite” – Dutch et al.
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Three types of Richter Magnitude
• ML = Local magnitude (the largest seismic wave regardless of type, P, S, SS)
• Mb = Magnitude is based on P wavesb – body wave
• Ms = magnitude is based on surface waves
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Moment Magnitude, Mw
• 1979; Thomas Hanks & Hiroo Kanamori
• not based on seismometer readings
• Based on seismic moment (Mo)
– Mo = average displacement on the fault x the
rupture area x rigidity of rock (i.e. shear
modulus ; resistance to shear stress)
• Mw = 2/3 log Mo – 10.7
• 10.7 is a constant
• Eg. Chilean earthquake (Mw=9.5 / M = 8.3)
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Earthquake Magnitude Classes
Earthquakes are also classified in categories ranging from minor to great,
depending on their magnitude
.
ClassMagnitude
Great 8 or more
Major 7 - 7.9
Strong 6 - 6.9
Moderate 5 - 5.9
Light 4 - 4.9
Minor 3 -3.9
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Modified Mercalli Intensity Index (MM)
Measure the damage and felt intensity
(observation)
Site examination and interviews;
photographic; Questionnaire.
Decrease from the epicenter
12 divisions of intensity
Intensity range I-XII (roman numerals)
Intensity II – felt by people
Intensity X – heavy damage !!!
Intensity map
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Intensity I : Not felt except
by a very few under
especially favorable
circumstances
Intensity III : Felt quite
noticeably indoors,
especially on upper floors
of buildings, but many
people do not recognise it
as an earthquake
Intensity XII : Damage
total. Waves seen on
ground surfaces. Objects
thrown upward into air
Ground acceleration during
earthquakes• measure of earthquake
acceleration on the ground
(i.e. how hard the earth
shakes)
• Important input parameter for
earthquake engineering –
bridge, building, etc.
• Expressed in g (the
acceleration due to Earth's
gravity) or in m s-2 (1 g = 9.81
m s-2).
• M 6-6.9 = acceleration 0.3 to
0.69g
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Man Made Earth Quake
• Building big dam or reservoir (Reservoir Induced Seismicity)
– Hoover Dam in US
• Load of water
• Infiltration of water into fractures/faults
• Magnitude 5
– Koyna, India 1962
• 6.5 quake in 1967 killed 177
• Disposing liquid waste into ground (disposal wells)
– 1986 quake in Ohio
– 1962—1965; Rocky Mountain Arsenal
– Strong correlation: amount of fluid and number of earthquakes
– Increase fluid pressure
• Underground nuclear explosions
– Earthquake M 5 to 6.3
Malaysia = Tasik Kenyir!!?
HAARP PROJECT
• Video
• China earthquake
caused by HAARP
weapon ???
• High Frequency
Active Auroral
Research Program
(HAARP)
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The amount of damage depends upon:-
• Geology– Mexico City earthquake; alluvium (lake deposits);
– but epicenter on solid rock; hundred kms away; M8.1
• Type of buildings– natural vibration frequency of the buildings vs
frequency of the seismic waves
• Magnitude
• Duration of shaking
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Effects of Earthquakes
• Primary effects
Caused directly by the phenomena
– Violent ground motion
– Surface rupture
– Permanent displacement / fault rupture
– Snap and uproot large trees and knock
people to the ground
– Shear/collapse large buildings; dams;
tunnels; pipelines; other rigid structure
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• Secondary effects
– Short range events:--• Tsunamis
• Liquefaction
• Landslides
• Fires
• Floods
– Long range effects:--• Regional subsidence
• Regional changes in groundwater level
Effects of Earthquakes
Mitigation Strategies
Mitigation Strategies:–
• Hazard Maps
• zoning, building
codes, emergency
plans
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Risiko dan Jangkaan Gempabumi
• (1) Jangka Panjang
– Kaedah keberangkalian utk menentukan
risiko kejadian gempa sepanjang satah
sesar / kawasan ttt
• Membantu perancangan guna tanah
(penempatan)
• Seismic hazard map (Peta risiko seismik)
– Paleoseismology
– Zon senyap seismik (seismic gap)
• Zon aktif sesar senyap (store tectonic strain)
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Probabilities and expected magnitudes of future California earthquakes
A diagram showing the probabilities and magnitudes of future earthquakes in California
from 1988 to 2018
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(2) Jangkaan jangka pendek:-
• Perubahan bentuk muka bumi
– Pengangkatan (uplift) yang berlaku
• Patterns and frequency of earthquakes
– (i) reduction in small/moderate
earthquakes prior to larger event
– (ii) small earthquake may tend to ring the
area.
• Foreshocks Water; Level in Wells; Emission
of Radon Gas
• Strange animal behavior
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Protective measures / mitigation
• Structural protection
• Land use planning
• Insurance
• Duduk diam dan tunggu !!
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