Wednesday, September 25, 2019

Earthquackes Essay Example | Topics and Well Written Essays - 2500 words

Earthquackes - Essay Example According to Stein and Wysession (217), earthquakes can also occur due to the elastic rebound theory, which says that in various situations energy is accumulated in rock that is being acted upon by tectonic forces to a degree that the energy rises above the bonding forces holding the rocks causing to break, suddenly returning to its original shape, and the crust moves violently as a result of the quickly released force. However, not all earthquakes are linked to with preexisting faults rather some are linked to intensely buried fold structures, volcanic environments among others in which the molten rock is forcefully pushing out of the crust. The cracking of a rock known as faulting leads to the discharge of energy when stored stress is rapidly transformed to movement and produces vibrations called seismic waves. These seismic waves then move outwards in all directions at a speed of nearly 14 kilometers per second, distorting the rocks they pass through, but the rock returns to its o riginal shape afterwards. The speed of seismic waves is dependent on the plasticity of the media they travel through such as rocks which portray elastic properties. In the event of external forces acting on the rock, they are forced to alter their shapes and since rocks just like other elastic materials, they have an elastic limit after which application of any additional force deforms the shape of the rock. Seismic Waves During earthquakes, the discharge of stress as energy leads to the creation of three different types of waves. The first one, primary waves or P-Waves is the fastest moving waves with the ability to pass through both liquid and solid rock, expanding and compressing the rocks as they move and are the first to be detected by seismographs (Qazi 78). The second type of waves created is the secondary waves or S-waves which unlike P-waves cannot pass through liquids. As these waves move, they are able to cut across the rocks they pass through at positions that are perpen dicular to the direction they are moving towards. Due to their large size in comparison to primary waves, S-waves are considered the most dangerous type of waves and they produce both vertical and horizontal motion as they travel. The seismic activity are terms used to describe the rate of occurrence, cause and magnitude of earthquakes an area experiences over a certain length of time, the instrument used to measure earthquakes is known as a seismometer while a device that not only measures but also records the magnitude is called a seismograph. Seismologists have come up with two scales of measurement to measure the quantitative magnitude of earthquakes one is the Richter scale, named after the American seismologist Charles Francis Richter. This scale is used to measure the movement of the land surface one hundred kilometers from the epicenter, the point on the Earth’s surface directly above the source of the earthquake, also known as the focus and can be as deep as seven hu ndred kilometers. However, quakes are not known to occur past this level since rocks are no not very firm at these higher pressures and temperatures. Smaller tremors are frequently experienced but these tremors usually cause little or no damage. The Richter scale is a logarithmic scale with a

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