Effect of earthquake

1. A PRESENTATION ON
EARTHQUAKE

2. Earthquake
• Earthquake, any sudden shaking of the ground caused by
the passage of seismic waves through Earth’s rocks.
Seismic waves are produced when some form of energy
stored in Earth’s crust is suddenly released, usually when
masses of rock straining against one another suddenly
fracture and “slip.” Earthquakes occur most often along
geologic faults, narrow zones where rock masses move in
relation to one another.

3. The Nature Of Earthquakes
• Causes of earthquakes
• Earth’s major earthquakes occur mainly in belts coinciding
with the margins of tectonic plates.
• The most important earthquake belt is the Circum-Pacific
Belt, which affects many populated coastal regions
around the Pacific Ocean—for example, those of New
Zealand, New Guinea, Japan, the Aleutian Islands,
Alaska, and the western coasts of North and South
America.

4. • It is estimated that 80 percent of the energy presently
released in earthquakes comes from those whose
epicentres are in this belt.
• A second belt, known as the Alpide Belt, passes through
the Mediterranean region eastward through Asia and joins
the Circum-Pacific Belt in the East Indies.
• The energy released in earthquakes from this belt is about
15 percent of the world total.

5. Natural forces
• Earthquakes are caused by the sudden release of energy
within some limited region of the rocks of the Earth.
• The energy can be released by elastic strain, gravity,
chemical reactions, or even the motion of massive bodies.
• Of all these the release of elastic strain is the most
important cause, because this form of energy is the only
kind that can be stored in sufficient quantity in the Earth to
produce major disturbances.
• Earthquakes associated with this type of energy release
are called tectonic earthquakes.

6. Tectonics
• A tectonic earthquake occurs when strains in rock masses
have accumulated to a point where the resulting stresses
exceed the strength of the rocks, and sudden fracturing
results.
Volcanism
• A separate type of earthquake is associated with volcanic
activity and is called a volcanic earthquake.
• There is a clear correspondence between the geographic
distribution of volcanoes and major earthquakes,
particularly in the Circum-Pacific Belt and along oceanic
ridges.

7. Artificial induction
• Earthquakes are sometimes caused by human
activities, including the injection of fluids into deep
wells, the detonation of large underground nuclear
explosions, the excavation of mines, and the filling of
large reservoirs.
• In the case of deep mining, the removal of rock
produces changes in the strain around the tunnels.

8. Reservoir induction
• Of the various earthquake-causing activities cited above,
the filling of large reservoirs is among the most important.
• Reservoir-induction effects are most marked for reservoirs
exceeding 100 metres (330 feet) in depth and 1 cubic km
(0.24 cubic mile) in volume.
• Three sites where such connections have very probably
occurred are the Hoover Dam in the United States, the
Aswan High Dam in Egypt, and the Kariba Dam on the
border between Zimbabwe and Zambia.

9. Seismology and nuclear explosions
• In 1958 representatives from several countries, including
the United States and the Soviet Union, met to discuss
the technical basis for a nuclear test-ban treaty.
• Among the matters considered was the feasibility of
developing effective means with which to detect
underground nuclear explosions and to distinguish them
seismically from earthquakes.

10. Effects of earthquakes
• Earthquakes have varied effects, including changes in
geologic features, damage to man-made structures, and
impact on human and animal life. Most of these effects
occur on solid ground, but, since most earthquake foci are
actually located under the ocean bottom, severe effects
are often observed along the margins of oceans.

11. Ground Shaking
• Ground shaking is the most familiar effect of earthquakes.
• It is a result of the passage of seismic waves through the
ground, and ranges from quite gentle in small earthquakes
to incredibly violent in large earthquakes.
• In the 27 March 1964 Alaskan earthquake, for example,
strong ground shaking lasted for as much as 7 minutes!
• Buildings can be damaged or destroyed, people and
animals have trouble standing up or moving around, and
objects can be tossed around due to strong ground
shaking in earthquakes.

12. Ground Shaking
• Beside is an image of the
Cypress viaduct which
was part of Interstate 880
in Oakland, CA.
• The columns failed
partially in response to
ground shaking from the
17 October 1989 Loma
Prieta earthquake.
Image by H.G. Wilshire, U.S. Geological Survey

13. Ground Rupture
• Ground rupture is another important effect of earthquakes
which occurs when the earthquake movement along a
fault actually breaks the Earth's surface.
• Rupture causes problems for humans by, well, rupturing
things; pipelines, tunnels, aqueducts, railway lines, roads,
and airport runways which cross an area of active rupture
can easily be destroyed or severely damaged.

14. Ground Rupture
• Below is a classic picture of a scarp formed by the 16
December 1954 Dixie Valley earthquake (magnitude 6.8)
in Nevada.
Image by Karl V. Steinbrugge

15. Landslides
• Landslides are caused by earthquakes both by direct
rupture and by sustained shaking of unstable slopes.
• They can easily destroy buildings in their path, or block
roads and railroad lines, or take hilltop homes with them
as they tumble.
• They even can dam rivers on occasion, like in the 17
August 1959 Hebgen Lake earthquake (magnitude 7.1) in
Montana.

16. Landslides
• Below is an image of a large landslide which fell across
Highway 17 in the Santa Cruz Mountains after the Loma
Prieta earthquake.
Image by C.E. Meyer, U.S. Geological Survey

17. Tsunamis
• Tsunamis are a series of water waves caused when the
seafloor moves vertically in an earthquake and which can
travel vast distances in a short period of time.
• Tsunami speeds in the deep ocean have been measured
at more than 700 km/hr, comparable to some jet planes,
and when tsunamis reach shallow water near the coast,
they can reach heights of more than 27 meters (90 feet)!
• The safest thing to do if you hear a tsunami is coming is
to move to higher ground away from the beach as quickly
as possible.

18. Tsunamis
• Below is an image of a tsunami striking the coast in Hilo,
Hawaii.This tsunami was generated by a magnitude 7.8
earthquake in the Aleutian Islands on 1 April 1946.
Image by Mrs. Harry A Simms, Sr.

19. Soil Liquefaction
• 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 themselves.

20. Soil Liquefaction
• Below is a picture of the Kwangishicho Apartments in
Niigata, Japan.Three of the buildings (the white ones)
have tilted over due to liquefaction.
Image from CDMG.

21. Fires
• 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
itself.

22. Fires
• Below is a terrifying image of fire after the 1994
Northridge earthquake.
Image by Ken Lubas, Los Angeles Times

23. What are the earthquake safety rules?
Before an earthquake
1. 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.
2. Conduct occasional home earthquake drills so that your
family has the knowledge to avoid unnecessary injuries
and panic in the event of an earthquake.
3. Evacuate old damaged buildings as they are sure to
down first during the earthquake.

24. What are the earthquake safety rules?
4.Be aware to tackle situations of earthquake while at
home, driving a car or in a public place.
During the Earthquake
1. Do not panic.
2. Go to an open space away from the building. If not
possible, then take shelter under a desk, table, bench or
corner of walls.
3. Stay away from glass.

25. What are the earthquake safety rules?
4. Do not use candles, matches or open fires in the event of
an earthquake.
5. Try to stop as soon as possible while driving a car, and
stay inside only until the tremor stops.
After the Earthquake
1. Expect after shocks.
2. Turn off gas and electricity.
3. Do not use light matches, and avoid turning on switches
as there may be leaked gas which may catch fire.

26. What are the earthquake safety rules?
4. Do not go near by damaged buildings.
5. Keep away from rivers and sea shores as huge waves
may sweep in.