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Earthquake

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Earthquake.

An earthquake is an event when the ground shakes as a result of the breaking and shifting of rock under great pressure.  The vibrations caused by this shaking can cause deaths and severe property damage.  An earthquake can trigger a tsunami (tidal wave).  The cause of earthquakes is the constant movement of the plates of the earth's crust as a result of pressures building up in the mantle beneath the crust.  Scientists used to believe that earthquakes were caused by faults, but they now believe that faults in the crust are the damage resulting from movement in the earth's mantle below the crust.

The two difficulties scientists have had are establishing a method for measuring the magnitude and intensity of the earthquake, and finding a way to predict where and when a severe earthquake will occur so that the population of that location can be prepared for it.  The measurement method most people are familiar with is the Richter scale, devised by American seismologist Charles Richter (1900-85), which measures the magnitude of the quake.  It has started at about 2.5 and goes to 8 or 9, based on earthquakes measured by instruments and calculated by his formula to date.  The intensity of an earthquake as felt by people in the area of the quake is measured by the Modified Mercalli Intensity Scale.

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See also: tsunami

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Last Modified: Monday, June 30, 2008