Chapter 4 Eearthquake & human activities

Earthquake and Human Activities
Sophea Boeut
Geology and the Environment
1

Contents
• General Overview of Earthquake
• Earthquake Measurement
• Earthquakes and Loss
• Earthquake Prediction
• Seismic Hazard and Mitigation
• Survival Tips
2

General Overview of Earthquake
• What is the earthquake?
The result of abrupt movement on fault fractures in the earth's
crust releasing the energy created three types of wave motion:
S-wave, P-wave, and surface waves.
• The effects of earthquake vary upon the magnitude and
intensity. Earthquake may recur on the same location in
an interval of period. The devastation of lives, cities and
towns is one of the effects of earthquake.
3

• Normal fault
4
 Classification of Fault
• Reverse fault
• Right-lateral strike-slip fault
Road cut on 1-40
near Kingman
Sandstone strata
at Wasatch
Plateau, Utah
Plowed fiend,
Imperial Valley,
California

5
 Elastic rebound theory
Right-lateral offset of a
fence by 2.5 m, San
Andreas fault in 1906.

• How the waves generated?
Earthquake occurs when rock
underground suddenly breaks
along the fault, and release energy.
The focus is the point on the fault
where the rupture begin.
The Epicenter, a point directly
above the focus.
P-wave and S-wave (both are Body
waves) out from the focus as
spherical direction and strike the
earth’s surface, generating Surface
wave.
6

 Few kilometers below
earth’s surface,
 Deep one is between 300-
700 kilometers below the
surface,
 Not known below 700
kilometers.
7
 Earthquake foci:
https://sites.g
oogle.com/sit
e/geohazarde
arthquakegeo
logy/
http://opening.download/view.php?pic=http:
//thelovenote321.com/wp-
content/uploads/2014/09/love-note-ripple-
effect.jpg

P-wave:
Compress and expand in the
same direction of the wave
moves. Velocity: 300 m/s in
air, 300-1,000 m/s in soil, 5
km/s in solid rock.
8
 Elastic waves
S-wave:
Move in all direction
perpendicular to their travel
direction, produces ground
motion, travel only through
solid. Velocity is about 5.2 km/s.
Surface-wave:
Rolling motion at the ground
surface commonly caused
from L-wave and Rayleigh
waves. It is large amplitude,
and the most destructive of
the earthquake.

Earthquake Measurement
Seismometer & Seismometer
9
 Earthquake detectors
• Detecting and recording the
vibration of the earth’s crust.
• The recording on Seismograph is
not the earthquake
• First earthquake detector,
invented by a Chinese Scholar,
Chang Heng, A.D. 130.

Seismogram record data 10
 Earthquake detector

• P-wave
11
 Travel time of P-wave and S-wave
• S-wave

12
 Earthquake intensity scale:
• Modified Mercalli Scale (MM):
• Developed in 1931 by Harry
Wood and Frank Neumann.
• Based on the earthquake
damage.
• Intensities vary depending
on the locations.
• Earthquake intensity
represent in Isoseismal Map
and Community Internet
Intensity Map (CIIM).

13
Isoseismal Map
 Earthquake in Northridge, California, 1994:
• Identifying the area of
earthquake damage, weak rock
or soil.
• Useful to planners and safety
construction standards.
CIIM
• Web-based system based on Shaking and Damaging.
• Grouping the intensity, averaging and plotting
according to postal codes.
• Useful with sparse seismograph coverage area.
• More reliable in low shaking area.
(https://earthquake.usgs.gov/data/dyfi/)
 Earthquake intensity scale:
• Modified Mercalli Scale (MM):

Richter Magnitude scales (ML)
14
 Earthquake magnitude scale:
• Introduced in 1935 by Charle Richter
and Beno Gutenberg, California
Institute of Technology.
• Based on Seismic records.
• No earthquake M>8.9 yet.
• Rector Magnitude is the common
logarithm of the ground motion which
is 10 times difference for each
magnitude.
• Example:
 M4 => 10,000 Microns
(log10(10,000) = 4).
 M5 => 100,000 Microns.
 M6 => 1,000,000 Microns.

15
 Earthquake magnitude scale:
Moment Magnitude scales (MW or M):
• Developed in 1970s,
• The most widely used scale,
• Be able to measure the other release seismic
events,
• Mw = 2/3 log M0-10.7
M0 is seismic moment = Shear modulus of rock near
the fault X Average amount of slips X slip size area
(based on Wikipedia)

Earthquake events showing with Richter and Moment Magnitudes
16
 Earthquake magnitude scales:

17
Earthquake Magnitude and Energy release:
Richter Magnitude of
9 selected earthquake
(1906-1994)
Equivalent magnitude and energetic:
Human-caused events
Natural events
Large earthquake

18
Forensic use of seismic records

19
Earthquake map
http://www.isc
.ac.uk/iscgem/
overview.php

Earthquakes and Loss
20
Earthquakes Impact
Gujarat, India,
MW=7.7, 2001, at
8:46 A.M,
t = over 2 min
• Damage covered 50 km by 70 km,
• Collapses of most high-rises (anything more than 3 stories), and low-rises
(cobble-stone structures) => 400,000 home destroyed, (Bad quake,
worse building),
• More than 20,000 lives loss, injured 167,000,
• Total properties damage estimated at $7.4 billion.
Alaska, 2002, MW =
7.9
• Surface rupture length of 320 km,
• 20 houseboat damage, several bridges,
• 159 dead due to Tsunamis, and one injury,
• Total damage estimated as $20 – 56 millions.
Colima, Mexico,
2003, MW = 7.8
• Collapse of 150 old houses, no damage to modern high-rise building,
• 29 dead, 300 injured.
Northbridge,
California, MW=6.7,
1994, at 4:30 A.M,
t = 10-20 s
• No surface rupture due to Blind Thrust underground, but produced high
acceleration, damaged up to 125 km.
• 13,000 building damaged, 21, 000 dwelling units evacuated, 240 mobile
homes destroyed by fire, and 11 major freeway damaged at 8 locations,
• 57 dead, and 8,700 injured,
• Total properties damage estimated at $13-50 billion.

Earthquakes and Loss
21
 Usually earthquake doesn’t kill
people, but the collapsed buildings
do.
Total vertical
collapse as the result
of “Story Shift”,
Mexico City, 1985.
Structure damage of
1886 earthquake
along East Bay Street,
Charleston, California.
Part of collapse of a
fashion center,
Northridge,
California 1994.

World Earthquakes and their impacts
22

Earthquake Prediction
• The hottest area in geophysics and geological research in
1970s-1990s.
• Great potential for saving lives and reducing property damage.
• Good prediction giving the location, time, and magnitude of a
future earthquake.
• SO EARTHQUAKE CAN'T BE PREDICTED BECAUSE THE
EARTHQUAKE GENERATION MECHANISM IS COMPLICATED TO
PREDICT FOR THE STATE OF OUR KNOWLEDGE NOW.
23

Forecast:
• One-week forecast is realizable, but
no one year ahead.
• Evaluation the probability of a large
earthquake occurring on an active
fault zone based on measurement
plate tectonic motion.
 70% of at least M<6.7 striking the San
Francisco bay region between 2000 and
2030.
 Knowing this will help people make
informed decisions as they continue to
prepare for future quakes.
24
The threat of earthquakes extends across
the entire San Francisco Bay region, and a
major quake is likely before 2030.

25
Statistic Approach:
 Accomplishment a statistical probability
for future events of given magnitudes based
on the statistical evidence pertaining to past
earthquake in a region.
 The calculation may be done by
worldwide scale or on a local scale.
 Interval of 1000 years for M=8
earthquake => 2 times a year.
 Interval of 100 years for M=7 earthquake
=> 20 times a year.
 Interval of 10 years for M=6 earthquake
=> about 100 times a year.
Statistic approach of
Southern California

26
Geological method:
• Earthquakes tending to
recur along the active
faults.
– 6 earthquake occurred along
San Andrea Fault,
– Around M=5.6,
– Rupture lengths:13-19 km,
– Recurring about every 22
years,
– Probability was 95%
occurring between 1988 to
1993.
San Andrea Fault

27
Geological method:
• Paleoseismicity:
– A prediction by digging
trenches into marsh or
river sediments to
recording the past
earthquake events.
– Dating using 14C.
Prediction of disrupted marsh and
lake deposits along San Andrea Fault,
10 large events extending from A.D
650 to 1857, average recurrence
interval is 132 years.

28
Future shocks:
• A large earthquake following by thousands of smaller-
magnitude earthquakes.
 M = 4.0-5.0 of the main shock resulting nonintimidating for the aftershocks.
 M= 5.0-6.0 of the main shock resulting the slips at the causative fault and
other faults close to it.
 From Northbridge earthquake, seismologist were able to predict
the number of aftershocks by fitting an Equation.
An experience after shocks of
M= 5.0-6.0 Northridge
Earthquake in 1994:
Daily record of aftershocks of
M= 3.0-5.9 during 3 weeks
after the main shock.

29
Animal behaviors:
– Tientsin Zoo, China, 1969: 2 hours before the
M=7.4 earthquake, Tiger appeared depressed,
Pandas screamed, Turtles were restless, and the
Yak would not eat.
– Haicheng, China, 1975: 1 and a half months
before the M=7.3 earthquake, Snakes came out
of hibernation; 1-2 days before, Pigs would not
eat and they climbed the walls, 20 min before,
Turtles jumped out of the water and cried.
– Tokyo, Japan, 1855: 1 days before the M=6.9
earthquake, wild Cats cried, and Rats
disappeared.
– Concepcion, Chili, 1835: 1 hour and 40 min
before the earthquake, Flocks of sea bids flew
inland, and Dogs left the city.
This doesn’t
appear to every
earthquake and Abnormal
animal behavior is not
always followed by an
earthquake.

Seismic Hazard and Mitigation
30
 Ground shaking
• S-wave and Surface
wave mainly
caused horizontal
damaging motion.
 Impact:
Horizontal ground
shaking
Strong horizontal
acceleration motion
deformed a house.
M=6.3 of earthquake in
1983 deformed a house,
Coalinga, California.
Cripple-wall deformed
M=6.9 of Loma
earthquake in 1989,
Watsonville, California

31
 Ground shaking
1. Building codes:
First defense against earthquake
damage.
Reduce damage and loss of life.
• Strict earthquake design’s law
passed after the 1933 (Long Beach),
and 1971 (Sylmar) earthquakes.
 Ways to reduce effects :
Increase in Earthquake
building codes.

32
 Ground shaking
2. Seismic zoning
• Particular regions exist different horizontal acceleration.
• Base shear acceleration is expressed as percentage of the
Acceleration Gravity (g=9.8 m/s2).
• A fraction of 1 g in horizontal direction caused buildings to
separate from their foundations.
 Ways to reduce effects:

33
 Ground shaking
3. Seismic joints & Bolting frames to foundation:
• Diagonal bracing and blocking provides shear resistance.
• Bolting frames help to mitigate the shearing force damage.
• L-shaped structures reduce damage at the joint
 Ways to reduce effects:
Diagonal cross-members
and blocks resist
horizontal earth motion.
Plywood sheeting
forms a competent
shear wall, and
metal “L” braces
and bolts tie the
structures to the
foundation

34
 Landslides
• Hundred of landslides may be triggered by an earthquake
in a slide-prone area.
Valley fever in Ventura Country in
early 1994 following Northbridge
earthquake
• 1994 Northbridge earthquake:
Creating dust for several days
Damaging properties
Causing disease by breathing
impure air.
 Coccidioidomycosis (CM) or Valley
fever– Flu-like symptoms,
diagnosed to 166 people from
January 24 to March 15, 1994.
 Impact:

35
 Landslides
• Loma Prieta E.Q:
Land sliding in Santa Cruz Mountain and
adjacent parts of the California Coast
Ranges.
$10 millions damage to homes, utilities,
and transportation.
• An 1959 earthquake in the United States:
 Land sliding on Red Mountain above
Madison River
 26 people were killed.
 Created shock wave of the air lifted cars,
trees, and campers of ground.
 Impact:

36
 Ground or Foundation Failure
• Shaking caused:
 Liquefaction of quick clays
caused large ground crack
opening.
 Saturated sand to Consolidate.
 So overlying soils supported by
only pore pressure.
Building collapse due to soil
liquefaction, Niigata, Japan, 1964
Building settlement, earth dams to
fail and blowing out below surface
sand.

37
 Ground or Foundation Failure
• Ways to reduce effects:
 Geological data obtaining from water wells and deep
borehole drilling to locate the liquefiable soils or
layers.
 Susceptible liquefaction is less than 10 m (30 feet).

38
 Ground rupture and Change in ground level
• Fault displacement creates:
 Fault rupture
– Mw=7.3 of earthquake in
Colorado Desert of southern
California, occurred in 1992.
 Uplift or subsidence of
land
– An 1964 earthquake in Alaska
– Part of Alaska Gulf upward 11 m.

39
 Ground rupture and Change in ground level
 Locating the past rupture surfaces that may
reactivate by excavation trench across the fault
zone.

40
 Fire and Tsunamis
• Fire:
 Caused by ruptured gas lines or
fallen electric power lines.
 Water mains may also break
due to earthquake to difficulty
access the fire-fighting action.
 Immediately after a
quake, you should shut
off gas supply.
• Tsunamis:
 Tsunamis = great wave
in harbor.
 Hidden-hazard.
 Recording goes back to
200 years
 Wait for Chapter 10.

Survival Tips
We are now on Ring of the Fire
41http://www.isc.ac.uk/iscgem/overview.php

Survival Tips
• Before an earthquake:
42
Turn off the gas by
turning the valve end 90 0C.

Survival Tips
• During an earthquake:
– Remain calm and consider the consequence of your actions.
– If you are indoor, stay indoor and get under the desk, bed, or a
strong doorway.
– If you are outside, stay aways from the building, walls, power poles,
and other objects that could fall. If driving, stop your car in an open
area.
– Do not use elevators, and if you are in a crowded area, do not rush
for a door.
43

Survival Tips
• After an earthquake:
– Turn off the gas at the meter.
– Use portable radios for information.
– Check water supplies, remembering that there is after in water
heaters, melted ice, and toilet tanks. Do not drink waterbed or pool
water.
– Check your home for damage.
– Do not drive.
44

References
45
• Chapter 4 of Geology and the Environment
• https://earthquake.usgs.gov/static/lfs/data/pager/WaldEtAlEC
EESDYFI.pdf
• http://www.isc.ac.uk/iscgem/overview.php
• http://earthquake.usgs.gov
• https://www.wikipedia.org/
• https://www.usgs.gov/

Thanks for your attention!
46
Be prepared if your dog
dons a hard hat.

Chapter 4 Eearthquake & human activities

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie Chapter 4 Eearthquake & human activities

Ähnlich wie Chapter 4 Eearthquake & human activities (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Chapter 4 Eearthquake & human activities