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EARTHQUAKE AWARENESS PROGRAMME
Supported by:
Seismology Division
Ministry of Science & Technology
Govt. of India
Organized by:
Resource Development Centre, New Delhi
Resource Developemnt Centre,
New Delhi
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WHAT IS AN EARTHQUAKE
An earthquake is a vibration or oscillation of the
surface of the earth, ranging from a faint tremor to a
wild motion caused by a transient disturbance of the
elastic or gravitational equilibrium of the rocks at or
beneath the earth the surface. It forms of energy of
wave motion transmitted through the surface layer of
the earth in widening circles from a point of sudden
energy release.
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New Delhi
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INTERIOR OF THE EARTH
Thus, on the basis of seismic
investigation, the earth can be
divided into three major zones,
these are
 Crust
 Mantle
 Core
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New Delhi
3
CAUSES OF THE EARTHQUAKE
Earthquakes are caused mainly due to disequilibrium
in any part of the crust of the earth. A number of
causes have been assigned to cause disequilibrium or
isostatic imbalance in the earth’s crust such as:
Vulcanicity
Faulting
& elastic rebound theory
Hydrostatic pressure and anthropogenic causes
Plate tectonic theory
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New Delhi
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NATURE OF EARTHQUAKE
When a stone is thrown into the pool, waves spread
through the water in all directions. Similarly, waves
spread out through the earth when there is a sudden
localized disturbance of the rock. An earthquake is
one such type of disturbance. When an earthquake
occurs, the fracturing rocks emit SEISMIC WAVES,
which radiates in all directions from the focus.
 Waves:
These are of two types: Body waves & Surface Waves
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New Delhi
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Body Waves: The body waves are two types:
P-Waves:
Primary waves.
These are fastest,
compressional and
capable of
propogating through
both, the solid and
liquid media
S-Waves:
Secondary waves. These are
transverse, comparatively
slower and pass only through
solid media
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New Delhi
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Surface Waves: The body waves are two types:
L-waves:
Shear motion in
horizontal plane.
Rayleigh waves:
Motion in vertical plane.
Surface Waves are more disastrous than the Body
Waves.
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New Delhi
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 Shocks
The earthquake vibrations shake the ground even
hundreds of kilometers away. The shaking is strongest
at its source. When the vibrations are felt in the
bedrock and ground, they are called shocks. Some
earthquakes are preceded by smaller foreshocks,
and larger earthquakes are always followed by
aftershocks.
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New Delhi
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 Focus & Epicenter
EPICENTRE
Earth’s surface
FOCUS
MANTLE
The point where the earthquakes are generated is
called focus. The point on the earth’s surface, directly
above the focus, is called the epicenter .
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New Delhi
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CLASSIFICATION OF THE EARTHQUAKE
Each earthquake differs from the other and thus it
becomes difficult to classify all the earthquakes in
certain categories. Inspite of these limitations
earthquakes are classified on the basis of common
characteristics as given below:
1. On the basis of causative factors:
a.
Natural earthquakes: Natural earthquakes are
those which are caused by natural processes i.e. due
to endogenetic forces. These are further divided into
four subcategories
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New Delhi
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Volcanic
earthquakes
Tectonic earthquakes
Isostatic earthquakes
Plutonic earthquakes
b.
Artificial or man-induced earthquake or
anthropogenic earthquakes: Artificial or maninduced earthquake or anthropogenic earthquakes are
caused by human activities such as pumping of water
and mineral oil from underground aquifers and oil
reserves respectively, deep underground mining,
blasting of rocks by dynamites for constructional
purposes e.g. for the construction of dams and
reservoirs, roads etc., nuclear explosion, storage of
huge volume of water in big reservoirs etc.
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New Delhi
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Examples, 1931 earthquakes of Greece due to
Marathon Dam, 1936 earthquakes of Hoover Dam
(USA) due to Lake Mead, Koyna earthquake
(Maharastra, India) of 1967 due to Koyna reservoir etc.
2. On the basis of focus:
Guttenberg has divided the world seismic centres on
the basis of the depths of their foci into 3 types viz.
Shallow focus earthquakes – foci are located at
the depths from the ground surface to 70 km,
Intermediate focus earthquakes – foci at the
depths between 70 km to 300 km, and
Deep focus earthquakes – foci at the depths
between 300 km toResource
700 km.
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New Delhi
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3. On the basis of human causalities:
Earthquakes are grouped into 3 categories on the
basis of their hazardous impacts in terms of human
casualities.
Moderately hazardous earthquakes – when
human deaths caused by severe seismic tremors are
below 50,000 mark,
Highly hazardous earthquakes causing human
deaths ranging between 51,000 to 1,00,000 mark, and
Most hazardous earthquakes causing human
casualities above 1,00,000 mark.
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New Delhi
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INTENSITY OF THE EARTHQUAKE
It is based on the degree of damage occurred at the
Earth’s surface and on the people’s reaction to the
shock. Italian seismologists Prof. Guiseppe Mercalli
proposed the following scale to measure the intensity
of an earthquake.
Mercalli Intensity
Effects
I
Instrumental
Detected only by
seismograph
II
Feeble
Noticed only by
sensitive people
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New Delhi
Richter
Magnitude
3.5 to 4.2
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III
Slight
Like the vibrations due to 3.5 to 4.2
a passing lorry; felt by
people at rest, especially
an upper floors
IV
Moderate
Felt by people while
walking, rocking of loose
objects, including
standing vehicles
V
Rather strong
Felt generally: most
sleepers are awakened
and bells ring
VI
Strong
Trees away and all
suspended objects
swing, damage by
overturning and falling of
loose objects
Resource Developemnt Centre,
New Delhi
4.3 to 4.8
4.9 to 5.4
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VII
Very strong
General alarm, wall
cracks, plaster falls
VIII
Destructive
Car drivers seriously
disturbed, masonry
fissured, chimneys fall,
poorly constructed
buildings damaged
IX
Ruinous
Some houses collapse
where ground begins to
crack, and pipes break
open
X
Disastrous
Ground cracks badly,
many buildings
destroyed and railways
lines bent, landslides on
steep slopes
Resource Developemnt Centre,
New Delhi
5.5 to 6.1
6.2 to 6.9
7 to 7.3
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XI
Very disastrous
Few buildings remain
standing, bridges
destroyed, all services
(railways, pipes and
cables out of action),
great landslides and
floods
7.4 to 8.1
XII
Catastrophic
Total destruction, objects
thrown into air, ground
rises and fall in waves
>8.1
(maximum
known
8.9)
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New Delhi
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MAGNITUDE OF THE EARTHQUAKE
It is a numerical scale of magnitudes from 0 to 9,
proposed by Prof. Charles Richter of California
Institute of Technology in 1935. The idea of magnitude
was based on observed surface movements. The
magnitude of an earthquake is a measure of the
amount of energy released. Earthquake magnitudes
are based on direct measurements of the size
(amplitude) of seismic waves, made with recording
instruments (seismograph), rather than on subjective
observations of destruction. The total energy released
by an earthquake can be calculated from the
amplitude of the waves and distance from the
epicenter.
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New Delhi
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EFFECTS OF THE EARTHQUAKE
Loss
of life and property
Landslides and Avalanches
Development of fissures and cracks
Disturbances of groundwater circulation and
drainage pattern
Fires
Upwarp and downwarp of the crust
TSUNAMIS
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New Delhi
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WORLD DISTRIBUTION
Earthquakes are not randomly distributed over the
globe but they tend to occur in narrow continuous belt.
The most notable aspects of the distribution of
earthquakes in the world is their locating along a
narrow belt. There are three well-defined belts or
zones of seismic activity in the world, where most
earthquakes originate are identified. These
earthquake zones are:
The
Circum-Pacific Belt
The Mediterranean and Trans-Asiatic Belt
The Mid-oceanic Ridges and the African rift
system Belt
Resource Developemnt Centre,
New Delhi
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INDIA AND EARTHQUAKE
Seismic zonation map of country is guide to the
earthquake vulnerability of the region. India has been
divided into four zones with respect to severity of
earthquakes. Of this zone V is seismically the most
active and zone II is the least active. Delhi comes under
zone IV of seismic hazard map. Asiatic and Indian plates
where the process of mountain building is still in
progress due to the Asiatic plate is moving southward
whereas the Indian plate is moving northward and hence
the northern margin of the Indian plate is being
subducted below the Asian plate. The collision of Asiatic
and Indian plates and resultant subduction of Indian
plate and consequent folding and faulting and gradual
rise of the Himalayas at the rate of 50 mm per year
cause earthquakes of northern India, Tibet and Nepal
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New Delhi
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Seismic Zoning Map of India
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New Delhi
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PREDICTION OF AN EARTHQUAKE
The Astrologers and Mystics are the people who
predict an Earthquake, which has no scientific basis.
There is no scientific way to predict an earthquake.
However, continuous recording of small - scale
earthquakes is sometimes useful in prediction of a
major earthquake.
Resource Developemnt Centre,
New Delhi
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HOW CAN I PREPARE FOR AN EARTHQUAKE
Learn
first aid procedures.
Keep emergency items on hand, including first aid
kit, supply of important medicines, flashlight, batterypowered radio, batteries, some drinking water and
nonperishable food, tools to shut off utilities, and a fire
extinguisher.
Plan to be self sufficient for a minimum of 72 hours
after an earthquake or other major disaster.
Conduct an earthquake safety check of your house
periodically
Develop a family earthquake plan and
communication plan for those first hours after an
earthquake.
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New Delhi
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Learn
how to shut off all utilities in your home.
Avoid placing heavy objects on shelves or heavy
pictures on walls where they could fall during a quake.
Use bolts or straps to secure heavy items that might
topple over, such as a bookcase, china cabinet, or
water heater.
Avoid placing heavy objects on shelves or heavy
pictures on walls where they could fall onto a bed.
Keep flammable or hazardous liquids such as paints,
pest sprays, or cleaning products in cabinets or
secured on lower shelves.
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New Delhi
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WHAT SHOULD I DO DURING AN EARTHQUAKE
If you’re
Indoors, duck under a desk or sturdy table or stand
in a corner. If not near a desk or table, move against
an interior wall, and project your head with your arms.
Stay away from windows, bookcases, file cabinets,
heavy mirrors, hanging plants, and other heavy
objects that could fall. Watch out for falling plaster or
ceiling tiles. Stay under cover until the shaking stops.
In a high-rise building, do not use the elevators. Do
not be surprised if the fire alarm or sprinkler systems
activate.
Outdoors,
move to a clear area, away from trees,
signs, buildings, or downed electrical wires and poles.
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New Delhi
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On
a sidewalk near buildings, and there is no safe
haven from overhead wires or other hazards, duck
into a doorway to protect yourself from falling bricks,
glass, plaster, and other debris.
Driving, pull over to the side of the road and stop.
Avoid overpasses, power lines, and other hazards.
Stay inside the vehicle until the shaking is over.
In a crowded store or other public place, do not
rush for exits. Once the shaking stops, crowds trying
to rush to the exits may be more dangerous than the
earthquake itself.
In a wheelchair, stay in it. Move to cover, if possible,
lock your wheels, and protect your head with your
arms.
Resource Developemnt Centre,
New Delhi
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In
the kitchen, move away from the refrigerator,
stove, and overhead cupboards.
In a stadium or theater, stay in your seat and
protect your head with your arms. Do not try to leave
until the shaking is over. Then leave in a calm, orderly
manner.
In bed, hold on and stay there, protecting your head
with a pillow.
In a coastal area, move to higher ground.
In a mountainous area or near unstable slopes or
cliffs, be alert for falling rocks and other debris that
could be loosened by the earthquake.
After an earthquake, be prepared for aftershocks
Resource Developemnt Centre,
New Delhi
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WHAT TO DO AFTER AN EARTHQUAKE
Check
yourself for injuries and provide help injured
or trapped persons.
Report any fires, chemical hazards, gas leaks, or
broken water lines to your emergency personnel.
Stay out of damaged buildings and away from
damaged areas.
Wear shoes in all areas near debris and broken
glass.
Stay away from beaches. Tsunamis and seiches
sometimes hit after the ground has stopped shaking.
If you're at school or work, follow the emergency
plan or the instructions of the person in charge.
Resource Developemnt Centre,
New Delhi
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Clean
up spilled medicines, bleaches, gasoline, or
other flammable liquids immediately and carefully.
Open closet and cabinet doors cautiously.
Listen to radio (or television) for updated emergency
information and instructions.
Use battery-powered lanterns or flashlights to
inspect your home.
Do not use flame producing devices/open flame
appliances if gas leak is suspected.
Do not touch downed power lines or objects touched
by them.
Use the telephone only for emergencies
Expect aftershocks.
Resource Developemnt Centre,
New Delhi
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Resource Development Centre
New Delhi
Resource Developemnt Centre,
New Delhi
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