Name: Earthquake: Causes, Magnitude and Its Measurement
Uploaded: 2019-07-19
Duration: 5 min 17 s
Description: We all have surely learnt about earthquakes, usually through the media. Let us discuss the causes and magnitude scales, and learn how a seismograph measures them.

Question

How do you appreciate the efforts of scientists in developing an instrument to measure the intensity and detect the source of an earthquake?

Accepted Answer

An earthquake is caused by the violent movements of rocks deep inside the earth's crust. The disturbances or tremors originating from deep inside the earth during an earthquake shake the earth’s surface. This shaking produces waves on the surface of earth called seismic waves. The seismic waves can be detected on the ground with the help of a very sensitive instrument called a seismograph. The following figure shows a seismograph.

A seismograph consists of a pendulum with a metallic string hanging from a base attached to the earth’s surface. While vibrating, the string of the pendulum moves within the poles of a horseshoe magnet. A pen is attached on the bottom side of the pendulum’s bob. A graph paper rolled on a rotating drum is kept below the pen. When an earthquake occurs, its tremors cause the seismograph pendulum to oscillate. These oscillations are recorded by the movement of the pen of the graph paper kept below the pendulum’s bob. The power of an earthquake is expressed in terms of a magnitude on Richter scale. We have to be really thankful to the scientists who developed seismograph and Richter scale which helps us to measure the intensity of the earthquake and also detect the source of an earthquake.

How do you appreciate the efforts of scientists in developing an instrument to measure the intensity and detect the source of an earthquake?

Important Questions on Some Natural Phenomena

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