The document provides information about earthquakes, including: - Earthquakes are caused by the sudden release of energy from movement within the earth's crust. This movement occurs along faults. - Seismic waves travel outward from the earthquake epicenter/focus. There are two main types of seismic waves - body waves and surface waves. Body waves arrive first and can travel through solid earth, while surface waves cause the most damage. - Seismographs create seismograms to measure and record earthquake seismic wave activity. Proper preparation and safety measures can help reduce risks during earthquakes.

1. 1
Earthquake
Introduction:
Earthquake is the shaking or trembling of Earth’s surface caused by the sudden
release of energy. Focus is the point within Earth where the earthquake starts. Epicenter is
the location on the surface directly above the focus. Faults are fractures in Earth where
movement has occurred.
Causes:

2. 2
Most earthquakes are produced by the rapid release of elastic energy stored in rock that
has been subjected to great forces. When the strength of the rock is exceeded, it suddenly
breaks, causing the vibrations of an earthquake.
Seismic waves:
Seismic waves are the waves of energy caused by the sudden breaking of rock within
the earth or an explosion. They are the energy that travels through the earth and is recorded
on seismographs.
Types 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.
Body waves:
Traveling through the interior of the earth, body waves arrive before the surface
waves emitted by an earthquake. These waves are of a higher frequency than surface waves.
P waves:
The first kind of body wave is the P wave or primary wave. This is the fastest kind
of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can
move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and
pulls the rock it moves through just like sound waves push and pull the air. Have you ever
heard a big clap of thunder and heard the windows rattle at the same time? The windows
rattle because the sound waves were pushing and pulling on the window glass much like P
waves push and pull on rock. Sometimes animals can hear the P waves of an earthquake.
Dogs, for instance, commonly begin barking hysterically just before an earthquake 'hits' (or
more specifically, before the surface waves arrive). Usually people can only feel the bump
and rattle of these waves. P waves are also known as compressional waves, because of the
pushing and pulling they do. Subjected to a P wave, particles move in the same direction that
the wave is moving in, which is the direction that the energy is traveling in, and is sometimes
called the 'direction of wave propagation'.
S waves:
The second type of body wave is the S wave or secondary wave, which is the second
wave you feel in an earthquake. An S wave is slower than a P wave and can only move
through solid rock, not through any liquid medium. It is this property of S waves that led
seismologists to conclude that the Earth's outer core is a liquid. S waves move rock particles
up and down, or side-to-side--perpendicular to the direction that the wave is traveling in (the
direction of wave propagation).

3. 3
P wave S wave
Surface waves:
Travelling only through the crust, surface waves are of a lower frequency than body
waves, and are easily distinguished on a seismogram as a result. Though they arrive after
body waves, it is surface waves that are almost entirely responsible for the damage and
destruction associated with earthquakes. This damage and the strength of the surface waves
are reduced in deeper earthquakes.
Love waves:
The first kind of surface wave is called a Love wave, named after A.E.H. Love, a
British mathematician who worked out the mathematical model for this kind of wave in 1911.
It's the fastest surface wave and moves the ground from side-to-side. Confined to the surface
of the crust, Love waves produce entirely horizontal motion.
Rayleigh waves:
The other kind of surface wave is the Rayleigh wave, named for John William Strutt,
Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885. A
Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because
it rolls, it moves the ground up and down and side-to-side in the same direction that the wave
is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which
can be much larger than the other waves.

4. 4
Love wave Rayleigh wave
Seismogram:
Most seismographs today are electronic, but a basic seismograph is made of a drum
with paper on it, a bar or spring with a hinge at one or both ends, a weight, and a pen. The
one end of the bar or spring is bolted to a pole or metal box that is bolted to the ground. The
weight is put on the other end of the bar and the pen is stuck to the weight. The drum with

5. 5
paper on it presses against the pen and turns constantly. When there is an earthquake,
everything in the seismograph moves except the weight with the pen on it. As the drum and
paper shake next to the pen, the pen makes squiggly lines on the paper, creating a record of
the earthquake. This record made by the seismograph is called a seismogram.
Measuring earthquake:

6. 6
Dos and Don’ts:
What to Do Before an Earthquake:
 Repair deep plaster cracks in ceilings and foundations. Get expert advice if there are
signs of structural defects.
 Anchor overhead lighting fixtures to the ceiling.
 Follow BIS codes relevant to your area for building standards
 Fasten shelves securely to walls.
 Place large or heavy objects on lower shelves.
 Store breakable items such as bottled foods, glass, and china in low, closed cabinets with
latches.
 Hang heavy items such as pictures and mirrors away from beds, settees, and anywhere
that people sit.
 Brace overhead light and fan fixtures.
 Repair defective electrical wiring and leaky gas connections. These are potential fire
risks.
 Secure water heaters, LPG cylinders etc., by strapping them to the walls or bolting to the
floor.
 Store weed killers, pesticides, and flammable products securely in closed cabinets with
latches and on bottom shelves.
 Identify safe places indoors and outdoors.
o Under strong dining table, bed
o Against an inside wall
o Away from where glass could shatter around windows, mirrors, pictures, or where
heavy bookcases or other heavy furniture could fall over
o In the open, away from buildings, trees, telephone and electrical lines, flyovers and
bridges
 Know emergency telephone numbers (such as those of doctors, hospitals, the police, etc)
 Educate yourself and family members
 Have a disaster emergency kit ready
o Battery operated torch with extra batteries
o Battery operated radio
o First aid kit and manual
o Emergency food (dry items) and water (packed and sealed)

7. 7
o Candles and matches in a waterproof container
o Knife
o Chlorine tablets or powdered water purifiers
o Can opener.
o Essential medicines
o Cash and credit cards
o Thick ropes and cords
o Sturdy shoes
 Develop an emergency communication plan
o In case family members are separated from one another during an earthquake (a real
possibility during the day when adults are at work and children are at school), develop
a plan for reuniting after the disaster.
o Ask an out-of-state relative or friend to serve as the 'family contact' after the disaster;
it is often easier to call long distance. Make sure everyone in the family knows the
name, address, and phone number of the contact person.
 Help your community get ready
o Publish a special section in your local newspaper with emergency information on
earthquakes. Localize the information by printing the phone numbers of local
emergency services offices and hospitals.
o Conduct week-long series on locating hazards in the home.
o Work with local emergency services and officials to prepare special reports for people
with mobility impairment on what to do during an earthquake.
o Provide tips on conducting earthquake drills in the home.
o Interview representatives of the gas, electric, and water companies about shutting off
utilities.
o Work together in your community to apply your knowledge to building codes,
retrofitting programmes, hazard hunts, and neighbourhood and family emergency
plans.
What to Do During an Earthquake:
Stay as safe as possible during an earthquake. Be aware that some earthquakes are
actually foreshocks and a larger earthquake might occur. Minimize your movements to a few
steps that reach a nearby safe place and stay indoors until the shaking has stopped and you
are sure exiting is safe.
 If indoors
o DROP to the ground; take COVER by getting under a sturdy table or other piece of
furniture; and HOLD ON until the shaking stops. If there is no a table or desk near
you, cover your face and head with your arms and crouch in an inside corner of the
building.
o Protect yourself by staying under the lintel of an inner door, in the corner of a room,
under a table or even under a bed.

8. 8
o Stay away from glass, windows, outside doors and walls, and anything that could fall,
(such as lighting fixtures or furniture).
o Stay in bed if you are there when the earthquake strikes. Hold on and protect your
head with a pillow, unless you are under a heavy light fixture that could fall. In that
case, move to the nearest safe place.
o Use a doorway for shelter only if it is in close proximity to you and if you know it is a
strongly supported, load bearing doorway.
o Stay inside until the shaking stops and it is safe to go outside. Research has shown
that most injuries occur when people inside buildings attempt to move to a different
location inside the building or try to leave.
o Be aware that the electricity may go out or the sprinkler systems or fire alarms may
turn on.
 If outdoors
o Do not move from where you are. However, move away from buildings, trees,
streetlights, and utility wires.
o If you are in open space, stay there until the shaking stops. The greatest danger exists
directly outside buildings; at exits; and alongside exterior walls. Most earthquake-
related casualties result from collapsing walls, flying glass, and falling objects.
 If in a moving vehicle
o Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under
buildings, trees, overpasses, and utility wires.
o Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps
that might have been damaged by the earthquake.
 If trapped under debris
o Do not light a match.
o Do not move about or kick up dust.
o Cover your mouth with a handkerchief or clothing.
o Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available.
Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of
dust.

9. 9
Seismic zonation in India: