3. Acknowledgement
Information and pictorial illustrations to create this
work have been drawn from class notes, prescribed
text books and various internet resources. The
author gratefully acknowledges the same. Any
objections to the use of internet resources may
please be indicated to suddurocks@yahoo.in so that
the same can be removed from the illustrations used
in this file.
This presentation is created with the sole intention
of benefitting a large number of student community.
This may not be used for any commercial purpose.
14. Earthquake occurs due to sudden
transient motion of the ground as a result
of release of elastic energy in the matter of
few seconds.
15. The impact of the event is most traumatic
because it affects large area, occurs all on
a sudden and is sometimes unpredictable.
16. They can cause large scale loss of life and
property and disrupts essential services
such as water supply, sewerage systems,
communication, power, transport etc.
17. They not only destroy villages, towns and cities,
but the aftermath leads to destabilize the
economic and social structure of the nation.
24. In a divergent plate boundary, two plates
will move away from each other, causing
the ground to sink, forming rift valleys.
25. This will also cause earthquakes due to
the sinking of land.
26. In transform plate boundaries, where
earthquakes usually happen, two plates
move side by side in opposite directions.
27. • This will produce lots of friction
when the two plates come into
contact.
28. The ground will vibrate and the tremors
can be felt, however, not as strong as
those in convergent, as they definitely will
not exceed 8.5 on the Richter Scale.
30. The 'earthquakes' are produced when
buildings collapse, or there are bombings
such as an atomic bomb or other strong-
impact bombs.
31. Gas pipes that explode underground can
also cause shockwaves to be radiated out.
32. Earthquake-like seismic waves can also be
caused by explosions underground. These
explosions may be set off to break rock while
making tunnels for roads, railroads, subways, or
mines.
33. Effects of Earthquakes
Earthquakes produce various damaging effects
to the areas they act upon.
34. This includes damage to buildings and in
worst cases the loss of human life.
35. The effects of the rumbling produced by
earthquakes usually leads to the
destruction of structures such as buildings,
bridges, and dams.
38. ►Mechanical observation systems make it
possible to issue warnings to nearby
populations immediately after detection of
an earthquake.
39. Measuring Magnitude of
Earthquakes
The magnitude of most earthquakes is
measured on the Richter scale, invented
by Charles F. Richter in 1934.
40. The Richter magnitude is calculated from
the amplitude of the largest seismic wave
recorded for the earthquake, no matter
what type of wave was the strongest.
41. What to do during
Earthquakes
Stay as safe as possible during an
earthquake.
42. Be aware that some earthquakes are
actually foreshocks and a larger
earthquake might occur.
43. Minimize your movements to a few steps
to a nearby safe place and if you are
indoors, stay there until the shaking has
stopped and you are sure exiting is safe.
44. If indoors :
DROP to the ground; take COVER by
getting under a sturdy table or other piece
of furniture; and HOLD ON until the
shaking stops.
45. If there isn’t a table or desk near you,
cover your face and head with your arms
and crouch in an inside corner of the
building.
46. Stay away from glass, windows, outside doors
and walls, and anything that could fall, such as
lighting fixtures or furniture.
47. 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.
48. 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.
49. 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.
50. • Be aware that the electricity may go out or
the sprinkler systems or fire alarms may
turn on.
53. Move away from buildings, streetlights and
utility wires.
54. Once in the open, stay there until the
shaking stops.
55. If in a moving vehicle, stop as quickly as
safety permits and stay in the vehicle.
Avoid stopping near or under buildings,
trees, overpasses, and utility wires.
56. Proceed cautiously once the earthquake
has stopped. Avoid roads, bridges, or
ramps that might have been damaged by
the earthquake.
57. If trapped under debris, do not light a match, do
not move about or kick up dust, cover your
mouth with a handkerchief or clothing.
58. 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.
59. Facts of Earthquakes
The largest recorded earthquake in the
United States was a magnitude 9.2 that
struck Prince William Sound, Alaska on
Good Friday, March 28, 1964 UTC.
60. The largest recorded earthquake in the
world was a magnitude 9.5 (Mw) in Chile
on May 22, 1960.
61. • The first “pendulum seism scope” to
measure the shaking of the ground during
an earthquake was developed in 1751,
and it wasn’t until 1855 that faults were
recognized as the source of earthquakes.
62. ►It is estimated that there are 500,000
detectable earthquakes in the world each
year. 100,000 of those can be felt, and
100 of them cause damage.
63. ►It is thought that more damage was done
by the resulting fire after the 1906 San
Francisco earthquake than by the
earthquake itself.
64. From 1975-1995 there were only four
states that did not have any earthquakes.
They were: Florida, Iowa, North Dakota,
and Wisconsin.
65. Most earthquakes occur at depths of less
than 80 km (50 miles) from the Earth’s
surface.
66. Florida and North Dakota have the
smallest number of earthquakes in the
United States.
67. It was recognized as early as 350 BC by
the Greek scientist Aristotle that soft
ground shakes more than hard rock in an
earthquake.
68. In 1663 the European settlers experienced
their first earthquake in America.
69. Earthquakes are one natural calamity
which isn't dependent on the weather.
Therefore, earthquakes can occur whether
its the cold, hot or rainy season.
70. Advantages of Earthquakes
Earthquake pushes the land further up,
thus helping vegetation flourish. So it is
part of shaping the earth.
71. It also loosens and churns the soil, allowing
nutrients and minerals to be deposited evenly,
creating a very fertile soil.
