What is EARTHQUAKE?
• Earthquake refers to the result of a sudden
release of energy in the Earth's crust that
creates seismic waves. It may also refer to
sudden and violent shaking of the ground,
sometimes causing great destruction.
What CAUSES Earthquakes?
• An earthquake is caused by a sudden slip
on a fault. Stresses in the earth's outer layer
push the sides of the fault together.
Stress builds up and the rocks slips suddenly,
releasing energy in waves that travel through
the earth's crust and cause the shaking that
we feel during an earthquake. An EQ occurs
when plates grind and scrape against each
Types Of FAULT
The form of faulting depends upon the type of plate motion
and nature of rocks.
STRIKE SLIP Fault
Strike-slip faults are vertical (or nearly vertical) fractures where the blocks
have mostly moved horizontally. If the block opposite an observer looking
across the fault moves to the right, the slip style is termed right lateral;
if the block moves to the left, the motion is termed left lateral.
A thrust fault is a type of fault, or break in the Earth's crust across which there has been
relative movement, in which rocks of lowerstratigraphic position are pushed up and over
higher strata. They are often recognized because they place older rocks above younger.
Thrust faults are the result of compressional forces.
A fault in which the hanging wall has moved downward relative to the footwall.
Earthquake swarms are sequences of earthquakes
striking in a specific area within a short period of
time. They are different from earthquakes followed
by a series of aftershocks by the fact that no
single earthquake in the sequence is obviously
the main shock, therefore none have notable
higher magnitudes than the other.
When an earthquake occurs, the energy is
dissipated into the surrounding medium
through seismic waves.
Seismic waves are the waves of energy caused by
the sudden breaking of rock within the earth or an
They are the energy that travels through the earth
and is recorded on seismographs.
Type of Seismic waves
• There are several different kinds of seismic waves,
and they all move in different ways. The two main
types of waves are Body waves and Surface waves.
• Body waves can travel through the earth's inner
layers, but surface waves can only move along
the surface of the planet like ripples on water.
Earthquakes radiate seismic energy as both body
and surface waves.
P-waves; also known as primary waves or pressure waves
S-waves; also referred to as secondary or shear waves
• Love and Raleigh waves
HOW IS EARTHQUAKE
There are currently two “measuring” schemes used to
“quantify” or “qualify” the destructiveness or power of an
1) The Mercalli Intensity scale (it is qualitatively based)
2) The Richter Magnitude scale (it is quantitatively based)
HOW COMMON ARE
Magnitude (Richter Scale)
Number per Year
0 – 3.4
4.9 – 5.4
5.5 – 6.1
7.0 – 7.3
1 every 10 years
Shaking and Ground Rupture
• Shaking and ground rupture are the main effects created
by earthquakes, principally resulting in more or less
severe damage to buildings and other rigid structures.
• The severity of the local effects depends on the complex
combination of the earthquake magnitude, the distance
from the epicenter, and the local geological and
geomorphological conditions, which may amplify or
reduce wave propagation. The ground-shaking is
measured by ground acceleration.
Landslides and Avalanches
• Earthquakes, along with severe storms, volcanic
activity, coastal wave attack, and wildfires, can
produce slope instability leading to landslides,
a major geological hazard. Landslide danger may
persist while emergency personnel are attempting
• Earthquakes can cause fires by damaging electrical
power or gas lines. In the event of water mains
rupturing and a loss of pressure, it may also become
difficult to stop the spread of a fire once it has started.
For example, more deaths in the 1906 San Francisco
earthquake were caused by fire than by the earthquake
• Soil liquefaction occurs when, because of the shaking
water-saturated granular material (such as sand)
temporarily loses its strength and transforms from
a solid to a liquid. Soil liquefaction may cause rigid
structures, like buildings and bridges, to tilt or sink
into the liquefied deposits.
• Large waves produced by an earthquake or a submarine
landslide can overrun nearby coastal areas in a matter
• Tsunamis can also travel thousands of kilometers across
open ocean and wreak destruction on far shores hours
after the earthquake that generated them.
• Ordinarily, subduction earthquakes under magnitude
7.5 on the Richter scale do not cause tsunamis, although
some instances of this have been recorded. Most destructive
tsunamis are caused by earthquakes of magnitude 7.5 or more.
• Earthquakes may cause landslips to dam rivers, which
collapse and cause floods.
• The terrain below the Sarez Lake in Tajikistan is in
danger of catastrophic flood if the landslide dam
formed by the earthquake, known as the Usoi Dam,
were to fail during a future earthquake. Impact
projections suggest the flood could affect roughly 5
• An earthquake may cause injury and loss of life, road
and bridge damage, general property damage
(which may or may not be covered by earthquake
insurance), and collapse or destabilization (potentially
leading to future collapse) of buildings. The aftermath
may bring disease, lack of basic necessities, and higher
• Many methods have been developed for predicting the time
and place in which earthquakes will occur. Despite considerable
research efforts by seismologists, scientifically reproducible
predictions cannot yet be made to a specific day or month.
However, for well-understood faults the probability that a
segment may rupture during the next few decades can be
• Earthquake warning systems have been developed that can
provide regional notification of an earthquake in progress,
but before the ground surface has begun to move, potentially
allowing people within the system's range to seek shelter
before the earthquake's impact is felt.
Preparing for an Earthquake
1. Become familiar with earthquake terms.
Preparing for an Earthquake
2. Safeguard your home by:
• Bolting bookshelves, water heaters and cabinets
to wall studs.
• Anchoring things so that they will not move or fall
during an earthquake is the most important thing
you can do to make yourself safe. Keeping things in
place also means they will not break.
1. Get under a heavy table or desk and hold on,
or sit or stand against an inside wall.
2. Keep away from windows.
3. If indoors, stay indoors.
4. If outdoors, stay outdoors away from falling
debris, trees and power lines.
5. If in a car, stay in the car.
6. Many injuries occur when people act on their
impulse to run.
7. Train yourself to take cover where you are.
Responses Inside Buildings
during an Earthquake
1. Drop, cover, and hold on.
2. Get under a table.
3. If there are no tables, get under or down between rows of
chairs or against inner walls.
4. Do not stand in a doorway. Buildings today have so much
partitioning, much of which is temporary, that many
doorways are actually weak points. Doorways are not a
good solution in a group situation either.
5. If you have nothing to get under, sit down against an interior
wall or next to a chair, holding on if possible.
6. If you are in bed, it's best to stay there, hold on, and pull
the pillows over your head for protection.
7. If children are in another room, take cover in the closest
safe place and call to them to do the same.
Responses If You Are Outside
during an Earthquake
1. Outside, get away from buildings, walls, trees and power lines.
1. If you cannot get clear of hazards, getting back inside
a building is better than staying on the sidewalk.
2. Sidewalks next to buildings are among the worst places
2. In a car, ease off the accelerator and slow down carefully.
Do not stop on or under overpasses and bridges if you
can avoid them. Be aware of what traffic around you is
doing and act accordingly.
3. If you live in coastal areas, be aware of possible tsunamis.
1. Take basic precautions immediately after an earthquake.
In addition to those outlined in the General Family
Preparedness, Residential Fires and Hazardous Materials
Accidents sections you should:
2. Expect aftershocks.
3. Avoid using vehicles except in emergencies.
4. Check yourself for injuries and protect yourself by putting
on shoes, work gloves and any other protective gear at hand.
5. If the electricity is off, turn on a flashlight.
6. Once you are sure that you're all right, check the people
around you for injuries.
1. You might ask loudly, "Is everyone okay?" This will
also help calm people.
2. The types of injuries that happen most often in an
earthquake include cuts, bruises, fractures and
7. Check the entire building for structural damage and
chemical spills. Refer to the section on Hazardous Materials
Accidents for further response information.
8. Check chimneys for cracks and damage. The initial check
should be made from a distance. Have a professional inspect
the chimney for internal damage that could lead to fire.
26th January, 2001
Scale between 7.6 and 7.7
The 2001 Gujarat earthquake occurred on January 26, 2001,
India's 52nd Republic Day, at 08:46 AM local time (3:16 UTC)
and lasted for over two minutes. The epicentre was about 9 km
south-southwest of the village of Chobari in Bhachau Taluka of
Kutch District of Gujarat, India. The earthquake reached a
magnitude of between 7.6 and 7.7 on the moment magnitude
Scale and had a maximum felt intensity of X (Intense) on
theMercalli intensity scale. The quake killed around 20,000
people (including 18 in South eastern Pakistan), injured
another 167,000 and destroyed nearly 400,000 homes.