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L-WAVES:
THE MOVEMENT
OF THE EARTH:
ü The
molten magma in the earth moves inside the earth and causes the movement of the
earth.
ü A volcano
is a vent opening into the earth crust through which molten material erupts
abruptly.
VOLCANO |
ü Earth quakes
are the vibrations that cause in the earth.
ü The
place where the vibration begins is called focus.
ü Focus
is the origin of the seismic energy.
ü True
location of an earthquake and source of seismic waves is focus.
ü The
place above the focus on the surface is called epicentre.
ü More
damage at the epicentre and decreases gradually.
Reasons of Earth Quakes:
ü Plate Tectonic forces.
ü Earth Faulting
ü Earth Folding
ü Volcanic eruptions
ü Conduction of nuclear tests
ü Construction of large dams
ü Digging of mines and canals
|
There
are three types of earthquake waves.
o P
waves
o S
waves
o L
waves
P-WAVES:
ü P-Waves are also called Primary waves.
P WAVES |
ü These are also called longitudinal waves.
ü These are a type of elastic waves.
ü These waves are the fastest waves compared to S and L waves.
ü They can travel through gases, liquids and gases.
ü These waves pull and push the objects.
ü P-Waves are recorded by seismometer.
ü P-Waves arrive first to the record station.
Seismograph:
ü This is a sensitive instrument.
ü This is an instrument used to record the seismic waves.
ü This records the earth quakes that are thousands of kilometers
away.
Richter
Scale:
ü This is an instrument to record the intensity of the earth
quakes.
ü
The Richter scale has 0 to 10 points.
ü
Intensity Scale: This is developed by Mercalli of
Italy. This has 0 to 12 points.
|
S-WAVES
ü S-Waves are also called secondary waves.
ü These waves also move through the body of an object unlike the
primary waves.
ü These are also called transverse waves.
ü They travel only through solid medium.
ü They do not travel through the liquid.
ü S-Waves arrive second at the record stations.
ü Like P-Waves the S-Waves also travel the same distance.
ü The objects are moved side to side with S-Waves.
L-WAVES:
ü
These are
also called surface waves.
ü
L-waves are
also called Love waves and are named after British Geophysicist A.E.H. Love.
ü
L-waves
make the rock to move horizontally.
ü
These are
more destructive compared to the P and S waves.
ü
The
vertical displacement does not take place.
TSUNAMI:
ü
This is a
Japanese word.
ü
This means
Harbor wave.
ü
A tsunami
is a series of water waves that causes displacement of large volume of water.
ü
The most
important reason for Tsunami is the tectonic forces.
ü India
in the year 2007 unveiled an early tsunami warning system.
ü This
is the first of
its kind in the world.
ü This
will sound an alert 13 minutes after an undersea earthquake in two potential
source regions.
ü This
is set up at the Indian National Centre for Ocean Information Services (INCOIS)
in Hyderabad.
THE REGIONS THAT EXPERIENCE THE
EARTH QUAKE MOST
ü
The Circum pacific belt runs
through west coast of both North and South America, Aleutian Islands and other
islands in the same region.
ü
This region experience 68
percent of the total earth quakes.
ü
The Pacific zone is also called
‘Ring of Fire”.
RING OF FIRE |
ü
The term ring of fire is
related to volcanoes.
ü
The mid Atlantic region
experience 21 percent of the earth quakes.
ü
The Mid continental belt
experience 11percent of the earth quakes.
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