An earthquake is the shaking of the Earth's surface caused by a sudden release of energy in the Earth's lithosphere. This social science project discusses earthquakes, including what they are, their causes, effects, and protection against them. Some key points made are that earthquakes result from the movement of tectonic plates and built-up pressure being released. Their effects include ground shaking, ground ruptures, landslides, tsunamis, and fires. Protection involves earthquake-resistant building construction and safety precautions during shaking. Some of the deadliest earthquakes mentioned caused thousands of deaths, such as in Nepal in 2015 and Japan in 2011.
3. INDEX
o Introduction
o What is an earthquake?
o Terms related to earthquake
o Causes
o Effects of earthquake
o Protection against earthquakes
o Deadliest earthquakes
o bibliography
4. INTRODUCTION
Earthquake constitutes 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 around the world,
except in some places where earthquakes occur rarely. The
devastation of cities and towns is one of the effects of earthquake.
5. WHAT IS AN EARTHQUAKE?
An Earthquake (a.k.a. quake, tremor or temblor) is the shaking of the
surface of the Earth resulting from a sudden release of energy in the
Earth's lithosphere that creates seismic waves.
Earthquakes can range in size from those that are so weak that they
cannot be felt to those violent enough to propel objects and people into
the air, and wreak destruction across entire cities.
The seismicity, or seismic activity, of an area is the frequency, type,
and size of earthquakes experienced over a period of time.
6. The other destructive natural phenomena like
cyclones and lightning can be predicted in advance to
some extent. This is not so in the case of earthquakes.
Earthquake is a destructive natural phenomena which
can not be predicted in advance. Nobody can tell when
and where an earthquake will occur.
This unpridictable nature of earthquakes makes them
even more dangerous.
7. TERMS
RELATED TO
EARTHQUAKE
FOCUS: The point within the
earth where an earthquake
rupture starts.
EPICENTER: The point on the
Earth's surface that is directly
above the focus, the point where
earthquake or undergriund
explosion originates.
8. AFTERSHOCKS: Smaller
earthquakes that occur after the main
earthquake in the same place as the
mainshock. Aftershocks are linked to
the size of the mainshock and if this is
large can continue for many weeks,
months or years.
FAULT: A crack in the Earth's crust
along which the rocks slide. Faults are
found at the edges of the plates where
the crust is moving in different
directions.
FAULT PLANE: The planar (flat)
surface along which two blocks of the
earth's crust suddenly slip past one
another during an earthquake.
9. MAGNITUDE: A number that categorizes the
amount of energy released during an earthquake.
MAINSHOCK: The largest, main earthquake.
SEISMICITY : The intensity, frequency, and
distribution of earthquakes in a specific area.
SEISMOGRAPH: A very sensitive instrument that
can detect, measure and record ground vibrations
and their intensities during an earthquake.
10. CAUSES
The plates of earth's crust are made of huge rocks having rough edges. Due to
their highly rough edges, movement of two crust plates relative t one another
is not smooth. When the two huge plates of earth's crust slide past one
another, they rub against one another ferociously and the rocks on the edges
get entangled. This builds up the pressure between the two plates of crust.
When sufficient pressure has been built up between the two crushed plates,
the entangled rocks of the two crust plates break open suddenly with a big
jolt. This sudden release of tremendous amount of energy produces shock
waves which makes the earth shake.
When the two plates of the earths crust moving in opposite directions collide
with each other, then the ends of these crust plates buckle and fold forming
new mountains and causing earthquakes.
11. A separate type of earthquake is
associated with volcanic activity
and is called a volcanic
earthquake.
Yet it is likely that even in such
cases the disturbance is the
result of a sudden slip of rock
masses adjacent to
the volcano and the consequent
release of elastic strain energy.
12. STRENGTH OF
EARTHQUAKE
The intensity and strength of an earthquake is measured on Richter
scale, the scale invented by Charles Richter in 1935.
An earthquake of magnitude 1.5 on Richter scale is the smallest
earthquake that can be felt by us. An earthquake of magnitude 4.5
causes some damage but not much damage.
The earthquakes having magnitudes higher than 7 on Richter scale
are really destructive earthquakes causing great loss of life and
property.
13. o The Ring of Fire (a.k.a. the Pacific
Ring of Fire, the Rim of Fire
or the Circum-Pacific belt) is a region
around much of the rim of the Pacific
Ocean where many volcanic
eruptions and earthquake occur.
o About 76% of the Earth's seismic energy is
released as earthquakes in the Ring of
Fire.
o About 90% of the Earth's earthquakes and
about 81% of the world's largest
earthquakes occur along the Ring of Fire
14. EFFECTS OF
EARTHQUAKE
GROUND SHAKING
o 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.
o 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.
15. Ground Rupture
o Ground rupture is another important effect of
earthquakes which occurs when the earthquake
movement along a fault actually breaks the Earth's
surface
o Landslides
o 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. Tsunami
o 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
17. Fires
o Fires are a major source of damage after earthquakes. Ground
rupture and liquefaction can easily rupture natural gas mains and
water mains, both contributing to the ignition of fires and
hindering the efforts to control them.
o In the 1923 Kanto earthquake in Japan nearly 100,000 people died
over 70,000 of them due to fires which swept the area after the
earthquake.
Other Effects of earthquakes include:
o Loss of life and property
o Damage to infrastructure
o Damage to transport system
o Economic activities like agriculture, trade etc are severely affected.
18. PROTECTION
AGAINST EARTHQUAKES
Earthquakes are highly destructive and cannot be predicted. So it is
necessary that we take precautions.
o All the houses and other buildings in seismic zones should be
designed and constructed in such a way that they can withstand
major earthquake tremors.
19. o All buildings should have fire-fighting Equipements in
working.
o Objects such as heavy mirrors, photo frames, water heaters, glass
wares, glass bottles etc should be mounted securely on the walls at such
places in the house that they do not fall on people during an earthquake.
IF WE ARE AT HOME WHEN AN EARTHQUAKE OCCURS,
THEN...
o We should take shelter under a sturdy table or a kitchen
counter and stay there till the shaking stops. We should cover
our heads with our hands.
o We should stay away from glass windows that may shatter
dues to tremors.
o We should stay away from tall and heavy objects, so that if
they topple, they may not fall on us.
20. oDo not re-enter badly damaged buildings. Turn off the water, gas
and electricity.
oKeep calm. Don’t panick. Turn on the transistor radio and listen to
the instructions carefully.
oKeep away from electric poles, beaches and low banks of rivers.
oIf you are aware of people buried in the debris, tell the rescue
team.
Do not rush and try to worsen the situation.
oDo not drink water from open containors.
IF YOU ARE OUTDOORS WHEN AN EARTHQUAKE OCCURS...
o If we are in a car (or a bus) we shoul not come out of it. The car
should be driven slowly to a clear and safe place away from
buildings or trees.
21. SOME DEADLIEST EARTHQUAKES...
This Photo by Unknown author is
licensed under CC BY-SA.
The April 2015 Nepal earthquake killed nearly 9,000 people and
injured nearly 22,000. It occurred at 11:56 Nepal Standard Time
on 25 April 2015, with a magnitude of 7.8M or 8.1M.
22. .
On October 30 2020, the western province of İzmir,
Turkey was hit by a 6.6-7.0 earthquake that damaged
Izmir city. The earthquake was followed by a tsunami
which damaged coastal areas and towns of the
province. It was followed by over 1,400 aftershocks
with 43 of them being over a magnitude of 4.0 .
23. This Photo by Unknown author is licensed under
CC BY-NC.
A magnitude 9.0 earthquake
struck in the Pacific Ocean off the
northeast coast of the Tōhoku
region of Japan’s Honshu island
on March 11, 2011.
It Triggered a massive tsunami
that flooded more than 200
square miles of coastal land.
Waves were estimated to be as
high as 38 meters, the height of a
12-story building.
