1) Earthquakes are caused by the sudden release of energy in the Earth's crust from the slow movement of tectonic plates. They generate shock waves that radiate out from the epicenter. 2) Most earthquakes occur along plate boundaries and are measured on the Richter scale. Earthquakes above magnitude 7 can cause widespread damage depending on their depth and location. 3) Different types of seismic waves like P, S, R and L waves are generated by earthquakes and travel through the Earth causing shaking at the surface. Surface waves tend to be more destructive to buildings and infrastructure.

1. A PPT ON
EARTHQUAKES
BY: UMANG WALIA
UID:15BCS7041
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2. Earthquake?
Earthquake is a violent tremor in the earth’s crust, sending out a series of shock
waves in all directions from its place of origin or epicenter.
For instance, if you throw stone in a pond of still water, series of concentric 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 disturbances in the
earth’s crust may produce vibrations in the crust which travel in all directions from
point of disturbances.
Earthquakes constitute one of the worst natural hazards which often turn into
disaster causing widespread destruction and loss to human life.
Earthquake risk
Seismic risk = hazard x exposure x vulnerability x location
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3. Causes of Earthquake
Earthquakes are caused by sudden release of energy in rocks. Plates in the form of
rocks are moving very slowly and earthquake occur when moving plates grind and
scrape against each other. The point at which an earthquake originates is the focus or
hypocenter and the point on the earth’s surface; directly above this is epicenter. The
study of earthquake is called seismology.
The point within Earth
where faulting begins is the
focus, or hypocenter
The point directly above the
focus on the surface is the
epicenter
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4. Where Do Earthquakes Occur and How Often?
~80% of all earthquakes occur in the circum-Pacific belt
most of these result from convergent margin activity
~15% occur in the Mediterranean-Asiatic belt
remaining 5% occur in the interiors of plates and on
spreading ridge centers
more than 150,000 quakes strong enough to be felt are
recorded each year
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5. Strength of earthquake
The intensity and strength of an earthquake is measured
on Richter scale, the scale invented by Charles Richter
California, USA in 1935, which categories earthquake on
the basis of energy released
The Richter magnitude scale, assigns a single number to quantify the amount
of seismic energy released by an earthquake. It is a base-10 logarithmic scale
obtained by calculating the logarithm of the combined horizontal amplitude
of the largest displacement from zero on a Wood–Anderson torsion
seismometer output. So, for example, an earthquake that measures 5.0 on
the Richter scale has a shaking amplitude 10 times larger than one that
measures 4.0. The effective limit of measurement for local magnitude is
about ML = 6.8.
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6. The amount of energy released during different categories of Richter
scale earthquake as follows:
Intensity of earthquake
(Richter scale
Energy release (amount of
TNT)
1.0 170 grams
2.0 6 kilograms
3.0 179 kilograms
4.0 5 metric tons
5.0 179 metric tons
6.0 5643 metric tons
7.0 1,79,100 metric tons
7.5 One megaton
8.0 5,64,300 metric tons
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7. The Economics and Societal Impacts of EQs
Building collapse
Fire
Tsunami
Ground failure
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8. What are Seismic Waves?
Response of material to the arrival of energy
fronts released by rupture
Two types:
Body waves
P and S
Surface waves
R and L Body Waves: P and S waves
Body waves
P or primary waves
fastest waves
travel through solids, liquids, or gases
compressional wave, material movement is in the same
direction as wave movement
S or secondary waves
slower than P waves
travel through solids only
shear waves - move material perpendicular to wave
movement
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9. Surface Waves: R and L waves
Surface Waves
Travel just below or along the ground’s surface
Slower than body waves; rolling and side-to-side
movement
Especially damaging to buildings
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10. Hazardous Effects of Earthquake
- Loss of life and property
- Damage to infrastructure
- Topographical changes
- Damage to transport system i.e. roads, railways, highways, airports, marine.
- Chances of fire short-circuit.
- Chances of Floods – Dams and Embankments can develop cracks
- Chances of outburst of epidemic
- Water pipes, sewers are disrupted
- Communications such as telephone wires are damaged.
- Economic activities like agriculture, industry, trade and transport are severely affected.
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11. Date Place m Scale
Sept.2 , 1993 Latur
(maharashtra)
6.3 Large areas of Maharashtra rocked.
10,000 people lost lives
May 22, 1997 Jabalpur
(Maharashtra)
6.0 40 person killed and over 100 injured
March 29, 1999 Nandprayag 6.8 widespread destruction in chamoli ,
rudraprayag and other areas. Massive
loss of human life
Jan. 26 2001 Bhuj (gujrat) 7.8 Tremors left by India and its
neighboring countries. Over 1 lakh
people killed. Huge loss to property
and infrastructure
Oct. 8, 2005 Muzzaffarabad
in Pakistan
occupied
Kashmir
7.4 Heavy damage to life and property.
Death toll about one lakh in Pakistan
and nearly 2000 in India
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12. Picture of search and rescue phase of Latur earthquake 1993
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13. Helpless man being trapped under debris
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14. Post – disaster picture from Kashmir earthquake 2005
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15. Earthquake Prediction
- Unusual animal behaviour
- Changes in water level
- Temperature change
- Large scale fluctuations of oil flow from oil wells
- Foreshocks or minor shocks before major earthquake
- Changes in seismic wave velocity.
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17. Earthquake safety rules
If you are in a house
don’t use lift for getting down from building
be prepared to move with your family
If you are in shop, school, office or theater
Don’t run for an exit. Stampede could prove fatal
take cover under a desk/table
move to corner or side walls
move away from window glass
Do not go near electric points and cable. Keep away from weak portion of the
building and false ceiling
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18. After an Earthquake
Keep calm, switch on the transistor radio and obey instructions.
Keep away from beaches and low banks of river. A huge wave may sweep in
Expect aftershocks.
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 circuit
Use a torch.
If there is any fire, try to put it out or call fire brigade.
Immediately clean up any inflammable products that may spilled.
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19. Contd.
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.
Do not drink water from open containers without having examined it.
Eat something. You will better and more capable of helping other.
Do not re enter badly damaged buildings and do not go near damage structures.
Do not walk around the streets to see what is happening. Keep the streets clear so rescue vehicles can access
the roads easily.
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20. Can Earthquakes be Controlled?
Graph showing the relationship
between the amount of waste injected
into wells per month and the average
number of Denver earthquakes per
month.
Some have suggested that pumping
fluids into seismic gaps will cause
small earthquakes while preventing
large ones.
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