Earthquakes — Flashcards

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An earthquake is a shock or series of shocks caused by a sudden movement of crustal rocks at a point called the seismic focus within the crust or mantle. It produces violent trembling of the ground.

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The seismic focus is the point within the Earth’s crust or mantle where a sudden movement of crustal rocks generates the earthquake. It is the origin point of the earthquake.

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The epicentre is the point on the Earth’s surface directly above the focus. Seismic waves reach the surface there first, and the intensity is maximum at that place.

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Effects of an earthquake are greater when the seismic focus lies near the surface because the waves travel a shorter distance before reaching the ground, so more energy is felt at the surface.

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Seismograph or Seismometer records the waves generated by an earthquake. It measures the seismic waves produced during the shaking.

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Seismology is the science of earthquakes. It studies earthquake causes, waves, measurement, distribution, and effects.

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The Richter Scale is an open-ended logarithmic scale used to estimate earthquake magnitude. It was devised by Charles F. Richter in 1935 and later modified in 1965 by Richter and Beno Gutenberg.

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It estimates the magnitude of an earthquake and gives an idea of the energy released at the earthquake centre. It has no fixed maximum or minimum, so it can be used for earthquakes of many sizes.