earthquakes
TRANSCRIPT
Disaster Management
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 [email protected] 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.
Contents :
Introduction to Earthquakes
Causes of Earthquakes
Effects of Earthquakes
Predictability of Earthquakes
• Measuring the Magnitude of Earthquakes
►What to do during an Earthquake
►Facts of Earthquakes
Advantages of Earthquakes
Pictures of Earthquakes
Introduction to Earthquakes
Earthquakes are the most destructive of
natural hazards.
Earthquake occurs due to sudden
transient motion of the ground as a result
of release of elastic energy in the matter of
few seconds.
The impact of the event is most traumatic because it affects large area, occurs all on a sudden and is sometimes unpredictable.
They can cause large scale loss of life and property and disrupts essential services such as water supply, sewerage systems, communication, power, transport etc.
They not only destroy villages, towns and cities,
but the aftermath leads to destabilize the
economic and social structure of the nation.
Causes of Earthquakes
Earthquakes may be caused by moving plate
boundaries.
It is when there are convergent, divergent
or transform plate boundaries.
In a convergent plate boundary, two plates
will approach each other.
• The denser plate will then sub duct.
►Friction is produced and the ground shakes, depending on the strength of the quake, causing an earthquake.
►Shockwaves are radiated around the area, creating tremors.
In a divergent plate boundary, two plates will move away from each other, causing the ground to sink, forming rift valleys.
This will also cause earthquakes due to the sinking of land.
In transform plate boundaries, where earthquakes usually happen, two plates move side by side in opposite directions.
• This will produce lots of friction
when the two plates come into
contact.
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.
In some cases, earthquakes might be
man-made.
The 'earthquakes' are produced when buildings collapse, or there are bombings such as an atomic bomb or other strong-impact bombs.
Gas pipes that explode underground can also cause shockwaves to be radiated out.
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.
Effects of Earthquakes
Earthquakes produce various damaging effects
to the areas they act upon.
This includes damage to buildings and in
worst cases the loss of human life.
The effects of the rumbling produced by
earthquakes usually leads to the
destruction of structures such as buildings,
bridges, and dams.
• They can also trigger landslides.
Predictability of Earthquakes
►Although some scientists claim ability to predict earthquakes, the methods are controversial.
►Mechanical observation systems make it possible to issue warnings to nearby populations immediately after detection of an earthquake.
Measuring Magnitude of
Earthquakes
The magnitude of most earthquakes is measured on the Richter scale, invented by Charles F. Richter in 1934.
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.
What to do during Earthquakes
Stay as safe as possible during an earthquake.
Be aware that some earthquakes are
actually foreshocks and a larger
earthquake might occur.
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.
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.
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.
Stay away from glass, windows, outside doors
and walls, and anything that could fall, such as
lighting fixtures or furniture.
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.
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.
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.
• Be aware that the electricity may go out or
the sprinkler systems or fire alarms may
turn on.
►Do NOT use the elevators.
►If outdoors :
Stay there.
Move away from buildings, streetlights and
utility wires.
Once in the open, stay there until the
shaking stops.
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.
Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that might have been damaged by the earthquake.
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.
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.
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.
The largest recorded earthquake in the
world was a magnitude 9.5 (Mw) in Chile
on May 22, 1960.
• 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.
►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.
►It is thought that more damage was done by the resulting fire after the 1906 San Francisco earthquake than by the earthquake itself.
From 1975-1995 there were only four states that did not have any earthquakes. They were: Florida, Iowa, North Dakota, and Wisconsin.
Most earthquakes occur at depths of less than 80 km (50 miles) from the Earth’s surface.
Florida and North Dakota have the smallest number of earthquakes in the United States.
It was recognized as early as 350 BC by
the Greek scientist Aristotle that soft
ground shakes more than hard rock in an
earthquake.
In 1663 the European settlers experienced
their first earthquake in America.
Earthquakes are one natural calamity which isn't dependent on the weather. Therefore, earthquakes can occur whether its the cold, hot or rainy season.
Advantages of Earthquakes
Earthquake pushes the land further up, thus helping vegetation flourish. So it is part of shaping the earth.
It also loosens and churns the soil, allowing
nutrients and minerals to be deposited evenly,
creating a very fertile soil.
Pictures of Earthquakes
Thank You !!!
Compiled By :
Sudarshan . S . K .
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