Earthquake is a violent
tremor in the earth’s crest, sending out a series of shock waves in all
direction from its focus. The waves are
called Seismic Waves and the point from where these waves are
initiated is called Focus Point (hypocenter). Such waves move perpendicular and
reaches a point when they can be felt, it is called Epicenter; this is the
most affected/destructed part of the earth by earthquake. The field of study
that deals with the earthquake is called Seismology, and the scale on which
the earthquake is measured is called Richter scale.
Types
of Seismic Waves:
(i)
P waves: These waves are called primary waves. These waves
reach the crest before other types of waves so are called primary waves. P waves can travel in all the form of matter
i.e. Solid, Liquid. These are also known as longitudinal waves. These
are the highest speed waves about 7-8km/sec.
(ii)
S Waves: These are called secondary Waves. These waves reach
the crest after primary waves. They can’t travel in liquid matter and can only
travel in solid part of the earth. These are also known as Transverse Waves. Their speed is about 6-7km/sec. Both P and S waves jointly known as Body
Waves.
(iii)
L Waves: These are the most destructive waves, move with the
speed of 3-4Km/sec. Because of slower
speed they reach the earth’s crest at last.
Causes
of Earthquake:
(i)
Plate Tectonic Boundaries. Convergent and Transformational Boundaries.
(ii)
Volcanic Eruption.
(iii)
Man Made: Mining, drilling etc.
Effects
of Earthquake:
(i) Primary
Effects: Destruction of Roads, buildings, catching fire etc.
(ii) Secondary
Effects: Deceases, Tides, power-cut, tele-communicational
disturbance, transformational problems etc.
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