Suggest ways that earthquakes may be predicted. How successful has prediction been in recent years. Explain why earthquakes of similar magnitude may cause different amounts of damage according to location and historical context.
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Suggest ways that earthquakes may be predicted. How successful has prediction been in recent years. Explain why earthquakes of similar magnitude may cause different amounts of damage according to location and historical context. At 6:00 am on January 17, 1994, disaster struck southern California in the form of an earthquake that originated deep beneath the Santa Susana Mountains. Slippage occurred on a fault and the resulting earthquake damaged buildings and highways, ruptured gas lines, and created chaos in the largest metropolitan area in the western US. Every news organization had special reporters on the scene. Pictures of damage and fires as well as interviews with distraught victims formed a steady parade across television screens. Even the most jaded students were fascinated with the awesome power of the earth. One of the greatest challenges to seismologists is to be able to predict earthquakes with enough precision to minimize loss of life and economic hardship. In an ideal world, we would know where all active faults lie, when they will rupture, and the magnitude of the next earthquake expected.
Ground shaking causes most earthquake damage. The magnitude of an earthquake, distance to the earthquake focus, type of faulting, depth, and type of material are important factors in determining the amount of ground shaking that might be produced at a particular site. Where there is an extensive history of earthquake activity, these parameters can often be estimated; however, in many areas of Washington they are still poorly defined. The magnitude of an earthquake influences ground shaking in several ways. Large earthquakes usually produce ground motions with large amplitudes and long durations. In addition, large earthquakes produce strong shaking over much larger areas than do smaller earthquakes. The 1949 magnitude 7.1 Olympia earthquake produced ground shaking lasting 30 seconds and was felt over an area of 550,000 square kilometers. In contrast, the 1964 magnitude 8.3 Alaska earthquake produced ground shaking for about 300 seconds and was felt over an area more than five times larger. The distance of a site from an earthquake affects the amplitude of ground shaking.
Subsurface structures, such as sedimentary layers that vary in thickness or degree of consolidation, may increase ground motion by focusing seismic wave energy at a particular site. The curved surfaces of buried bedrock topography may also focus waves. Langston and Lee (1983) suggested focusing as a mechanism to explain why the severity of damage observed in West Seattle during the 1965 Seattle-Tacoma earthquake seemed unrelated to surface geology in many places. The depth to bedrock changes from very near the surface in the West Seattle area to significantly deeper just a short distance away in downtown Seattle. Earthquakes have always been a problem and will carry on to be. Predicting an earthquake is not easy and the problems that can be caused from an earthquake are immense. However over recent years with new technology and historical evidence prediction of earthquakes have improved. Damage caused by an earthquake can vary due to the type of buildings and the geologic structure of the area that the earthquake hits.
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