Question

The place below the earth’s surface from where the vibration starts is known as:
(a) Earthquake focus
(b) Earthquake center
(c) Earthquake epicenter
(d) Earthquake centrifugal

Answer 1

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Option (a)

Earthquake focus

The place below the earth’s surface from where the vibration starts is known as earthquake focus.

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• An earthquake is a sudden, rapid shaking of the earth caused by sudden displacement of the lithospheric plates or by volcanic activity.

• The point when the disturbance begins in the interior of the earth is called the focus.

• The point directly above it on the surface of the earth is called epicenter.

• On the surface, the greatest impact is felt at the epicenter.

• As we move away the strength of the seismic waves weakens and so it causes less damage.

• If the point of origin of an earthquake is underwater, that is the ocean floor then tectonic subduction tends to disturb the ocean surface and displaces huge amount of water that generates tsunami waves.

• The instrument used for recording and measuring the seismic waves is called seismograph.

• The graphical representation of ground motion below the instrument is called seismogram.

• The seismogram helps in determining the time, epicenter and focal depth of an earthquake.

Answer 2

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Earthquake focus

The location below the earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter. Sometimes an earthquake has foreshocks.