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Earthquakes � PAGE �5�




The major contributor that is involved in most of the geological formations on Earth is the plate margins. The plates have an approximate thickness of 100 kilometers. This is not very thick when compared to the radius of Earth, which is a radius of 6000 kilometers. The major plates are made up of continental and oceanic crust. When these plates move they produce earthquakes.

Earthquake Movement

Most of the time we hear about earthquakes everyday in the news. Exactly what makes an earthquake? An earthquake is produced when there is a sudden release of energy, which causes a violent shaking in the crust of the Earth. This release of energy is caused when there is a build up of stress of two lithospheric plates. When these to lithospheric plates slide against one another, friction will cause the plates not to move. Because these plates do not move, the stress that is exerted on them causes a change in shape of the plates. Over a period of time, the stress that is being exerted on the plates increases to a point that causes the plates to move suddenly, producing the earthquake. The stress that was built up is released through the earthquake, only to build up again in time. Most of the time earthquakes are produced along fault lines. A fault line exist where there is a crack in the crust of the Earth where there has been a movement of the plates (MSN Encarta, 2008).

Earthquake Measurement

The energy that is produced by an earthquake is transmitted through seismic waves. A seismograph is a machine that is used by scientist to detect and record the seismic waves. The seismograph is able to detect both horizontal motions and vertical motions of the movements of the ground. The seismograph records these movements as a set of lines, which are jagged. This record is known as a seismogram. Seismologist use different types of seismographs to record the information of different kinds of...
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