SARVAJANIK COLLEGE OF
Earthquakes occur as a result of global plate motion. However,
this simple picture is far from complete. Some plate boundaries
glide past each other smoothly, while others are punctuated by
catastrophic failures. Some earthquakes stop after only a few
hundred metres while others continue rupturing for a thousand
kilometres. Earthquakes are sometimes triggered by other large
earthquakes thousands of kilometres away. We address these
questions by dissecting the observable phenomena and
separating out the quantifiable features for comparison across
events. We begin with a discussion of stress in the crust
followed by an overview of earthquake phenomenology,
focusing on the parameters that are readily measured by
current seismic techniques. We briefly discuss how these
parameters are related to the amplitude and frequencies of the
elastic waves measured by seismometers as well as direct
geodetic measurements of the Earth's deformation. We then
review the major processes thought to be active during the
rupture and discuss their relation to the observable parameters.
We then take a longer range view by discussing how
earthquakes interact as a complex system. Finally, we combine
subjects to approach the key issue of earthquake initiation. This
concluding discussion will require using the processes
introduced in the study of rupture as well as some novel
mechanisms. As our observational database improves, our
computational ability accelerates and our laboratories become
more refined, the next few decades promise to bring more
insights on earthquakes and perhaps some answers.
Table of Contents
1.2 Terms Related To Earthquake
2.2 Surface Cause
2.3 Tectonic Cause
2.4 Volcanic Cause
3.1 Body Waves
Primary (P) Waves
Secondary (S) Waves
3.2 Surface waves
4.0 Strength Of Earthquake……………………….
9.0 Case Study (Earthquake of Bharuch,Gujrat2001)……..………….25
Earthquakes constitute one of the worst natural hazards
which often turn into disaster causing widespread destruction
and loss to human life.
The effects of earthquake vary upon the magnitude and
intensity. Earthquakes occur every now and then all round the
world, except in some places where earthquakes occur rarely.
The devastation of cities and towns is one of the effects of
An earthquake is a trembling or a shaking movement of
the ground, caused by the slippage or rupture of a fault within
the Earth's crust. A sudden slippage or rupture along a fault line
results in an abrupt release of elastic energy stored in rocks that
are subjected to great strain. This energy can be built up and
stored over a long time and then released in seconds or minutes.
Strain on the rocks results in more elastic energy being stored
which leads to far greater possibility of an earthquake event.
The sudden release of energy during an earthquake causes lowfrequency sound waves called seismic waves to propagate
through the Earth's crust or along its surface.
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 other. In California
there are two plates the Pacific Plate and the North American
Plate. The Pacific Plate consists of most of the Pacific Ocean
floor and the California Coast line. The North American Plate
comprises most the North American Continent and parts of the
Atlantic Ocean floor. These primary boundary between these
two plates is the San Andreas Fault. The San Andreas Fault is
more than 650 miles long and extends to depths of at least 10
miles. Many other smaller faults like the Hayward (Northern
California) and the San Jacinto (Southern California) branch
from and join the San Andreas Fault Zone. The Pacific Plate
grinds northwestward past the North American Plate at a rate of
about two inches per year. Parts of the San Andreas Fault
system adapt to this movement by constant "creep" resulting in
many tiny shocks and a few moderate earth tremors. In other
areas where creep is NOT constant, strain can build up for
hundreds of years, producing great EQs when it finally releases.
Dam destroyed by an earthquake
1.1 What is Earthquake?
“An Earthquake is the result of a sudden release of energy in
the earth’s crust that creates seismic waves.”
The seismic activity of an area refers to the frequency,type
and size of earthquakes experienced over a period of time.
If you throw stone in a pond of still water,series of waves
are produced on the surface of water,these waves spread out in
all directions from the point where the stone strikes the water.
similarly, any sudden disurbances in the earth’s crust may
produce vibration in the crust which travel in all direction from
point of disturbances.
1.2Terms Related To Earthquake
the top layer of the earth, which consists of solid rock.
Both the continental crust (land masses) and oceanic crust (the
land beneath the ocean) belong to the crust.
Hypocentre or Focus:
It is the point within the earth, from where seismic
rupture(breaking of rocks) occurs and the location from which
seismic waves are released.
It is the point on the surface of the earth, vertically
above the place of origin (hypocenter) of an earthquake. This
point is expressed by its geographical Coordinates in terms of
latitude and longitude.
It is the vertical distance between the Hypocentre
(Focus) and Epicentre.
A Fault line is the surface trace of a fault, the line of
intersection between the earth’s surface.
Fault plane:Fault plane are the crackes or sudden slips of the
A Fault scrap is the topographic expression of faulting
attributed to the displacement of the land surface by movement
An objective measure of the strength of an earthquake.
vibrations that move through the earth in a way similar
to waves moving in water. They can travel through solids and
2.Causes Of Earthquake
The primary cause of an earthquake is faults on the crust of the
“A fault is a break or fracture between two blocks of
rocks in response to stress.”
There is a chicken and egg relationship between
faults and earthquakes
Faults allow the blocks to move relative to each other.
This movement may occur rapidly, in the form of an earthquake
- or may occur slowly, in the form of creep. Faults may range in
length from a few millimeters to thousands of kilometers. Most
faults produce repeated displacements over geologic time.
During an earthquake, the rock on one side of the fault suddenly
slips with respect to the other. The fault surface can be
horizontal or vertical or some arbitrary angle in between.
Earth scientists use the angle of the fault with respect to
the surface (known as the dip) and the direction of slip along
the fault to classify faults.
Faults which move along the direction of the dip plane
are dip-slip faults and described as either normal or reverse,
depending on their motion. Faults that move horizontally are
known as strike-slip faults and are classified as either rightlateral or left-lateral. Faults, which show both dip-slip and
strike-slip motion are known as oblique-slip faults.
1. Normal fault:
a dip-slip fault in which the block above the fault has
moved downward relative to the block below. This type of
faulting occurs in response to extension and is often
observed in the Western United States Basin and Range
Province and along oceanic ridge systems.
2. Thrust (reverse)fault:
a dip-slip fault in which the upper block, above the
fault plane, moves up and over the lower block. This type of
faulting is common in areas of compression, such as regions
where one plate is being sub ducted under another as in
Japan. When the dip angle is shallow, a reverse fault is often
described as a thrust fault.
3. Strike-slip fault:
a fault on which the two blocks slide past one
another. The San Andreas Fault is an example of a right
A left-lateral strike-slip fault is one on which the
displacement of the far block is to the left when viewed
from either side.
A right-lateral strike-slip fault is one on which the
displacement of the far block is to the right when viewed
from either side.
Some major causes of earthquakes on basic of its
2.2 Surface Cause
coasts,dashing of sea waves, avalanches , railway trains, heavy
tremors.some of them are man made,other are natural.
2.3 Tectonic Cause
Structural disturbances resulting in the
parts of the
lithosphere is the main cause of this type of earthquake. Most
of the disastrous earthquakes belong to this category and occur
in areas of great faults and fractures. Sudden yielding to strain
produced on the rocks of accumulating stress causes
displacements especially along old fault zones known as great
2.4 Volcanic Cause
Earthquakes related to volcanic activity may produce
hazards which include ground cracks, ground deformation, and
damage to manmade structures.
There are two general categories of earthquakes that can
occur at a volcano:
long period earthquakes.
Earthquakes produced by stress changes in solid rock
due to the injection or withdrawal of magma (molton rock).
These earthquakes can cause land to subside and can produce
large ground cracks. These earthquakes can occur as rock is
moving to fill in spaces where magma is no longer present.
Volcano-tectonic earthquakes don't indicate that the volcano
will be erupting but can occur at anytime.
Long period earthquakes:
It is produced by the injection of magma into
surrounding rock. These earthquakes are a result of pressure
changes during the unsteady transport of the magma. When
magma injection is sustained a lot of earthquakes are produced
(Chouet, 1993). This type of activity indicates that a volcano is
about to erupt. Scientists use seismographs to record the signal
from these earthquakes. This signal is known as volcanic
3.Types Of Waves
Seismic waves produced due to earthquake are basically
divided into two major types:
3.1 Body waves:
Two types of body wave are there:
Primary (P) Wave:
• The faster of these body waves is called the
primary or P wave.
• Its motion is the same as that of a sound wave
in that, as it spreads out, it alternately pushes
(compresses) and pulls (dilates) the rock.
These P waves are able to travel through both
solid rock, such as granite mountains, and
liquid material, such as volcanic magma or the
water of the oceans.
Secondary (S) Wave:
• The slower wave through the body of rock is
called the secondary or S wave.
As an S wave propagates, it shears the rock
sideways at right angles to the direction of
• If a liquid is sheared sideways or twisted, it
will not spring back.
• S waves cannot propagate in the liquid parts of
the earth, such as oceans and lakes.
3.2 Surface Wave:
Surface waves travels parallel to the earth’s surface and
these waves are slowest and most damaging. Surface wave are
divided into following types:
• Its motion is essentially that of S waves
that have no vertical displacement.
• it moves the ground from side to side in a
horizontal plane but at right angles to the
direction of propagation.
• The horizontal shaking of Love waves is
particuly damaging to the foundations of
• Love waves generally travel faster than
• Love waves (do not propagate through
water) can effect surface water only
insofar as the sides of lakes and ocean bays
pushing water sideways like the sides of a
It’s Like rolling ocean waves.
Rayleigh waves wave move both vertically
and horizontally in a vertical plane pointed
in the direction in which the waves are
• Rayleigh waves, becasuse of their vertical
component of their motion can affect the
bodies of water such as lakes.
4.Strength Of Earthquake
Earthquake intensity varies. Some are so minor that they
can only be felt at the epicenter. Other earthquakes are so strong
that it shakes hundreds of thousands of square miles.
Scientists measure the strength of earthquakes using
machines known as seismographs, which record the trembling
of the ground. This instrument is simply a pen that traces a
straight line on a turning drum. When the earth moves, the pen
is jolted out of its normal course, and traces a wiggle on the
paper beneath it. A very sensitive seismograph can magnify the
tiniest tremors one million times. The stronger the earth’s
movement, the larger the wiggle is drawn.
Using the information from the seismograph, scientists
determine its strength using a magnitude scale known as the
Richter Scale. The official definition of the magnitude of an
“the logarithm to base ten of the maximum seismicwave amplitude (in thousandths of a millimeter) recorded on a
standard seismograph at a distance of 100 kilometers from the
Amount of energy released during different
Intensity Of Earthquake
On Richter Scale:
Energy Release (Amount
5 Metric Tons
179 Metric Tons
5643 Metric Tons
179100 Metric Tons
1 Mega Tons
564300 Metric Tons
4.1 Seismometers-The measurement of earthquake
Seismometers are instruments that measure motions of
the ground, including those of seismic waves generated
by earthquakes, volcanic eruptions, and otherseismic
Seismometers may be deployed at Earth's surface, in
shallow vaults, in boreholes, or underwater.
A complete instrument package that records seismic
seismographs continuously record ground motions
around the world to facilitate the monitoring and
analysis of global earthquakes and other seismic
makes tsunami warnings
waves travel considerably faster than tsunami waves.
Seismology is the scientific study of earthquakes and the
propagation of elastic waves through the Earth.
5.Types Of Zones
The Geological Survey of India (G. S. I.) first published
the seismic zoning map of the country in the year 1935. With
numerous modifications made afterwards, this map was initially
based on the amount of damage suffered by the different
regions of India.because of earthquakes.
Color coded in different shades of the color red, this
map shows the four distinct seismic zones of India. Following
are the varied seismic zones of the nation, which are
prominently shown in the map:
Zone – II
This is said to be the least active seismic zone.
This region is liable to MSK VI or less and is classified
as the Low Damage Risk Zone.
Zone - III:
This zone is classified as Moderate Damage Risk
Zone which is liable to MSK VII. and also 7.8 The IS
3.The Andaman and Nicobar Islands, parts of Kashmir,
Western Himalayas fall under this zone.
Zone - IV:
This zone is called the High Damage Risk Zone
and covers areas liable to MSK VIII. The IS code
assigns zone factor of 0.24 for Zone 4. The IndoGangetic basin and the capital of the country (Delhi),
Jammu and Kashmir fall in Zone 4. In Maharashtra the
Patan area (Koyananager) is also in zone 4.
Zone - V:
Zone 5 covers the areas with the highest risks
zone that suffers earthquakes of intensity MSK IX or
greater. The IS code assigns zone factor of 0.36 for Zone
5. It is referred to as the Very High Damage Risk Zone.
The state of Kashmir,the western and central Himalayas,
the North-East Indian region and
Kutch fall in this zone.
the Rann of
Earthquake prediction is usually defined as the
specification of the time , location , and magnitude of a future
earthquake within stated limits.
But some evidence of upcoming Earthquake are
Unusual animal behavior
Water level in wells
Large scale of fluctuation of oil flow from oil wells
Foreshocks or minor shocks before major earthquake
Uplifting of earth surface
Change in seismic wave velocity
7.Effect Of Earthquake
Most earthquake-related deaths are caused by the
collapse of structures and the construction practices play a
tremendous role in the death toll of an earthquake.Some
primary effect of earth quack are following:
Loss of life and property
Damage to transport system i.e. roads, railways,
highways, airports, marine
Damage to human infrastructure.
Communications such as telephone wires are damaged.
Water pipes, sewers are disrupted
Economic activities like agriculture, industry, trade and
transport are severely affected.
Secondary effects are the after-effects of the earthquake,
such as fires, tidal waves, landslides and disease,lend
The shocks produced by earthquakes particularly
in hilly areas and mountains which are tectonically
sensitive causes landslides and debris fall on human
settlements and transport system on the lower slope
segments, inflicting damage to them. Occasionally large
landslides can be triggered by earthquakes. In 1970 an
earthquake off the coast of Peru produced a landslide
than began 80 miles away from the earthquake. The
slide was large (it's height at about 30 meters or 100
feet), traveled at more than 100 miles per hour and
plowed through part of one village and annihilated
another, killing more than 18,000 people.
Shaking and ground rapture
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
measured by ground acceleration.
Ground rupture is a visible breaking and
displacement of the Earth's surface along the trace of the
fault, which may be of the order of several metres in the
case of major earthquakes. Ground rupture is a major
risk for large engineering structures such as dams,
bridges and nuclear power stations.
earthquakes strongly shake the buildings and thus
causing severe fires in houses, mines and factories
because of overturning of cooking gas, contact of live
electric wires, churning of blast furnaces, displacement
of other fire related and electric appliances.
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. For example, in the 1964 Alaska
earthquake, soil liquefaction caused many buildings to
sink into the ground, eventually collapsing upon
earthquake( measuring more than 7 on richter scale)
travelling through sea water generate high sea waves and
cause great loss of life and property.fig shows the tsunami
of the 2004 Indian ocen earthquake.
A flood is an overflow of any amount of water that
Floods occur usually when the volume of water
within a body of water, such as a river or lake, exceeds the
total capacity of the formation, and as a result some of the
water flows or sits outside of the normal perimeter of the
body. However, floods may be secondary effects of
earthquakes, if dams are damaged. Earthquakes may cause
landslips to dam rivers, which collapse and cause floods.
8. Earthquake Safety Rules
Before an earthquake
Ensure that water heaters and gas appliances are firmly
fixed and shut off when not in use, as they can cause fire
hazards during an earthquake.
Conduct occasional home earthquake drills so that your
family has the knowledge to avoid unnecessary injuries
and panic in the event of an earthquake.
Evacuate old damaged buildings as they are sure to
down first during the earthquake.
Be aware to tackle situations of earthquake while at
home, driving a car or in a public place.
If you are in house;
Don’t use lift for getting down from
Be prepared to move with your family.
If you are in shop ,school or office;
Don’t run for an exit.
Take cover under a disk/table.
Move away from window glass.
Do not go near electric point and cable.
Keep away from weak portion of the
building and false ceiling.
After the Earthquake
• Keep calm, switch on the transistor radio and obey
Keep away from beaches and low banks of river. A huge
wave may sweep in.
Do not re enter badly damaged buildings and do not go
near damage structures.
Turn off the water, gas and electricity.
Do not smoke, light match or use a cigarette lighter.
Do not turn on switches there may be gas leak or short
If there is any fire, try to put it out or call fire brigade.
Do not drink water from open containers without having
If you aware of people have been buried, tell the rescue
team. Do not rush and try not to worsen the situation.
Avoid places where there are loose electric wires and do
not come in contact with any metal object.
Eat something. You will better and more capable of
Do not walk around the streets to see what is happening.
Keep the streets clear so rescue vehicles can access the
Some major Earthquake of india:
Large areas of Maharashtra rocked.
10,000 people lost lives.
40 person killed and over 100
widespread destruction in
chamoli , rudraprayag and other
areas. Massive loss of human life.
Tremors left by India and its
neighboring countries. Over 1 lakh
people killed. Huge loss to
property and infrastructure.
Heavy damage to life and property.
Death toll about one lakh in
Pakistan and nearly 2000 in India.
Earthquake Case study: Bhuj Earthquake 26th
A Powerful Earthquake of magnitude 6.9 on Richter-Scale
rocked the Western Indian State of Gujarat on the 26th of
January, 2001. It caused extensive damage to life & property.
This earthquake was so devastating in its scale and suffering
that the likes of it had not been experienced in past 50 years.
Leaving thousands seriously injured, bruised and handicapped;
both physically, psychologically and economically.
The epicenter of the quake was located at 23.6 north
Latitude and 69.8 east Longitude, about 20 km Northeast of
Bhuj Town of the Kutch district in Western Gujarat. At a depth
of only 23 kms below surface this quake generated intense
shaking which was felt in 70% region of India and far beyond in
neighbouring Pakistan and Nepal too. This was followed by
intense after shocks that became a continued source of anxiety
for the populace.
The Seismicity of the affected Area of Kutch is a known
fact with a high incidence of earthquakes in recent times and in
historical past. It falls in Seismic Zone V. The only such zone
outside the Himalayan Seismic Belt. In last 200 years important
damaging earthquakes occurred in 1819, 1844, 1845, 1856,
1869,1956 in the same vicinity as 2001 earthquake. Twenty-one
of the total 25 districts of the state was affected in this quake.
Around 18 towns, 182 talukas and 7904 villages in the affected
districts have seen large-scale devastation. The affected areas
even spread up to 300 km from the epicentre.
In the Kutch District, four major urban areas – Bhuj,
Anjar, Bachau and Rapar suffered near total destruction. The
rural areas in the region are also very badly affected with over
450 villages almost totally destroyed.
In addition, wide spread damages also occurred in
Rajkot, Jamnagar, Surendranagar, Patan and Ahmedabad
districts. Other Urban areas such as Ganhidham, Morvi, Rajkot
and Jamnagar have also suffered damage to major structures,
infrastructure and industrial facilities. Ahmedabad the capital
was also severely affected.
Date: 26 January 2001
Origin line: 08 hrs.46 min. 42.9 sec. IST
Epicenter: Latitude 23.40° N Longitude 70.28°E
Focal Depth: 25 kms.
On the morning of January 26, 2001, the Nation’s
52nd Republic Day, a devastating earthquake occurred in the
Kutchh district of the state of Gujarat. The earthquake was felt
as far away as Delhi in the north, Kolkata in the east. Bhuj
town and the village Bhachau, 60 km east of Bhuj, were the
worst affected and many other areas of Gujarat including its
state headquarters Ahmedabad, were badly affected.
Damage assessment :
There were more than 20,000 deaths and 167,000 people
Four districts of Gujarat lay in ruin and altogether, 21 districts
Around 300,000 families and at least 3 million children
aged 14 and under were affected.
Around 600,000 people were left homeless.
In the city of Bhuj, more than 3,000 inhabitants of the
city lost their lives; the main hospital was crushed and
close to 90% of the buildings was destroyed.
There was significant damage to infrastructure with
facilities such as hospitals, schools, electric power and
water systems, bridges and roads damaged or destroyed.
Fig (a): Damage to high rise building in
Fig (b): 5 year old girl recovers at
a hospital in Bhuj on Monday after
Friday's massive earthquake.