Such news items raises several questions like
What are earthquakes?
How do they occur?
What are the causes and effects?
Can we prevent them?
Can we predict them?
Earthquakes-causes and effects
Prof. D Chandrasekharam
Department of Earth Sciences
Head, Centre of Studies in Resources Engineering
Indian Institute of Technology Bombay
Earth structure and Interior
Continental
drift
Earth structure and Interior
Plate boundaries
Pacific ridge
Indian Ocean
Ridge
Atlantic ridge
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Plate boundaries
Plate boundaries
Constructive boundary
Destructive boundaries
Himalayas
Sumatra
Japan
Continental crust
California
Ocean crust
Types of collision tectonics
Pakistan Earthquake 7.2M
Subduction
Continent-Continent
Earthquake foci
Earthquakes in 2005
Ring of
Fire
2
Indian Ocean Floor
Types of faults
Mumbai
10 Ma
Fracture
38 Ma
55 Ma
75 Ma
Earthquake terms
Locating an earthquake
Seismograph
USA
Japan
Bombay
Arrival of “P” wave
Tectonic map of India
Arrival of “S” wave
Seismic Profile
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Earthquake Magnitude
TNT Equivalent
Richter
TNT for Seismic
Magnitude
Energy Yield
Earthquake Severity
Richter Magnitude
Earthquake Effects
Less than 3.5
Generally not felt, but recorded.
3.5-5.4
Often felt, but rarely causes damage.
5.4 - 6.1
At most slight damage to well-designed buildings.
Can cause major damage to poorly constructed
buildings over small regions.
6.1-6.9
Can be destructive in areas up to about 100 kilometers
across where people live.
7.0-7.9
Major earthquake. Can cause serious damage over larger
areas.
8 or greater
Great earthquake. Can cause serious damage in areas
several hundred kilometers across.
Sumatra
-1.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
6 ounces
30 pounds
320 pounds
1 ton
4.6 tons
29 tons
73 tons
1,000 tons
5,100 tons
32,000 tons
80,000 tons
1 million tons
5 million tons
32 million tons
7.5
8.0
8.5
9.0
10.0
12.0
160 million tons
1 billion tons
5 billion tons
32 billion tons
1 trillion tons
160 trillion tons
Example
(approximate)
Breaking a rock on a lab table
Large Blast at a Construction Site
Large Quarry or Mine Blast
Small Nuclear Weapon
Average Tornado (total energy)
Little Skull Mtn., NV Quake, 1992
Double Spring Flat, NV Quake, 1994
Northridge, CA Quake, 1994
Hyogo-Ken Nanbu, Japan Quake, 1995; Largest
Thermonuclear Weapon
Landers, CA Quake, 1992
San Francisco, CA Quake, 1906
Anchorage, AK Quake, 1964
Chilean Quake, 1960
(San-Andreas type fault circling Earth)
(Fault Earth in half through center,
OR Earth's daily receipt of solar energy)
Volcanoes and earthquake foci-Indonesia
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Can we predict an earthquake?
Science has not reached that
stage as yet!!
Thank You
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