Raffles Junior College
JC 1 Physical Geography
Earthquakes
Supplementary Pointers
Effects of Earthquakes

Tsunami (e.g. Indian Ocean Tsunami): It is a large wave caused by an abrupt displacement of
water. Water does not travel with the wave but moves up and down as the wave passes.
High crests and low troughs. Usually the wave trough arrives to the shore first, causing the
sea level to drop, exposing the seabed. Soon the crest arrives flooding the coastal area. Most
tsunamis are generated when the sea floor abruptly deforms and vertically displaces the
overlying water. This may be caused by earthquakes or submarine volcanic eruption.

Liquefaction (e.g. Niigata, Japan / Mexico City): Occurs when water-saturated sediment is
reorganized because of violent shaking. The sediment collapses, expelling water and causing
the ground surface to subside. The shaking can suspend sand grains in waterlogged soil so
that they lose contact and friction with other grains. Soil in a state of liquefaction has no
strength and cannot bear any load. A liquefied sand layer can shoot to the surface through
cracks, forming a sandblow/sandboil, depositing sand on the ground. With all the material
forced to the surface, the surrounding area sinks unevenly causing buildings to topple.

Fire may be a serious problem in earthquakes because water lines may be broken by the
quakefiremen cannot put our fires with low water pressure (Kobe 1995)

Tall buildings will sustain the least damage if they are located directly at the epicenter
because they can withstand the P-waves while S-waves on the other hand, occur far away
from the epicenter. Brick buildings are the most vulnerable. Mud-brick structures completely
disintegrate, burying people in piles of earth and dust, rather than trapping them in voids of
air pockets between building slabs, as in a concrete building collapse.

A seiche is a standing wave in a body of water. It is caused by resonances in a body of water
disturbed by seismic activity. They are tide-like rises and drops in water levels in lakes.

Earthquakes may change water levels in wells, indicating a shift in underground fluid
pressure.

Landslideshampered relief as roads were blocked

Death (loss of economically active individuals) and injuries

Destruction of buildings (homes and industries) homeless and joblesspovertypeople
turning to selling organs and prostitution to make a living.

Damage to infrastructureelectricity and phone lines knocked out, railways and roads
damaged

Damage to economy (due to a combination of other effects)
o
decline in tourism
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o
Trade deficitincreased borrowing leading to national debtshampers economic
growth
o
Failure of businesses (communications interrupted, production stoppageloss of
revenueunemploymentclosure)

Shortage of clean waterwater contaminated

Diseases rampant

Psychological trauma (Fear and panic)social disorder

Environmental pollutionspread of sewage and industrial chemicals
Management of Earthquakes


Earthquake prediction:
o
Unusual animal behavior (e.g. missing cats and dogs). No scientific evidence.
o
Changes in well water level, water content (muddy) (Tangshan Earthquake)
o
Tiltmeter: measures the tilt of the earth’s surface, similar to spirit level.
o
Seismic monitoring by the network of seismic stations all over the world.
o
Recurrence Interval: Large fault ruptures require the build-up of great stress, many
years pass between repeated surface ruptures on a single fault.
o
Foreshocks: used to predict whether a more damaging shock will follow.
o
Using GPS systems to monitor shifts in rock (San Andreas fault)
Mitigation:
o
Build earthquake-proof buildings using the isolated base technology. It involves
using a coil and placing it between the structure and the foundation of the building
to counteract the motion of seismic waves. Building can stay nearly stationary as the
support moves opposite in direction to the earthquake motion. Cross-supports in
between frame supports or the corners of the frame hold the structure together.
(Japan)
o
Hazard mapping: It is probabilistic approach taken to show hazard occurrence level.
It takes into consideration the uncertainties in size and location of earthquakes and
the resulting ground motions that can affect a particular site. It is used to identify
areas prone to hazards such as liquefaction, landslides and ground shaking. These
maps are used by insurance companies to set premiums for property insurance. It
also help engineers to develop safety code for building construction (e.g. identify
safe locations for nuclear waste storage).
o
Controlled earthquakes: Water under high pressure can be pumped into the ground
to trigger earthquakes releasing stress accumulated in rocks. The water acts as a
lubricant, allowing rocks to move, causing earthquakes. Without water, rock strain
would build up until a large quake occurred. With water reducing friction, strain can
be released through smaller timed quakes.
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

o
Evacuation measures/warning system
o
Enforcement of building safety codesretrofitting of structures (Golden Gate Bridge,
San Francisco)
o
Replacing pipelines with semi-flexible material to prevent breakage and gaps pipes
with automatic shut-off valves. Circuit breakers to ensure a controlled supply of
electricity to minimize electrical fire.
o
Public educationearthquake drills and basic life support skills (Japan)
o
In Japan, setting up of “Large-scale Disaster and Emergency Medical Information
System”info about bed availabilities, capability of performing surgeryprevents
patient transfer from one hospital to another during a crisis
Earthquake response
o
Search and rescue
o
Immediate relief (medical, shelter, sanitation, food & water, communication (after
Kobe Earthquake, Japan, NTT and Motorola provided free telephone service for
victims), social order, psychological support)
o
Some countries refused international aid in light of protecting national pride
o
Setting up of Earthquake Memorial Park to preserved damaged state to remind
people to stay vigilant (Kobe Port)
o
Reconstruction and recovery and long-term development
Problems of Earthquake Hazard Management in LDCs
o
Population Size (densely populatedhigh death rates)
o
Lack of Preparedness

People are preoccupied with working to make ends meet due to their state
of povertythus they view dealing with natural disasters as a lower priority

Low literacy rate and poor educationunaware of earthquakes
o
Low technologyNo money to invest in earthquake prediction equipment such as
the tiltmeter and warning systems
o
Lack of past records/datacannot predict future occurrences
o
Inaccurate prediction (e.g. animal behavior which is not scientifically proven)
o
Poor government

Does not view earthquakes as a problemput more emphasis on economic
development and tradeignoring plight of citizens

Weak leadership and indecisiveness

Unnecessary protocol and standard proceduresslow response to an
emergencyforeign aid may find it difficult to seek permission from an
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inefficient government (Indonesian government during Indian Ocean
Tsunami)

Corruptionself-interest
o
Poor building designlack of funds and certified engineerslow quality materials
and outdated building methods (Kashmir Earthquake)
o
Poor infrastructure/Communications networksome locations are inaccessible to
aid, telephone network disrupted
o
Resistance towards foreign aiddoes not want to depend on otherswants to be
self-reliant
o
Poor Living conditions  slum areas are unhygienicovercrowding facilitates
rampant spread of diseases. Povertyincreased crime and social disorder
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