| Summary: | 碩士 === 國立成功大學 === 地球科學系碩博士班 === 91 === By analyzed the postseismic surface displacement pattern to study the relaxation time of lower crust and asthenosphere with numerical simulation; and also use the data acquired from Global Positioning System to compare with result of numerical simulation to study the difference between observation and simulation that caused by main shock, after shock or the velocity of plate motion, etc. In this article we divide the Chelungpu fault into five parts and each part has different parameters in rupture that also used as the control factor of numerical simulation.
According to the numerical simulation, we get the convergent pattern of postseismic displacement field from south to north, and the maximum horizontal displacement is 50.39 cm at the station of M402, while the minimum horizontal displacement is 3.15 cm at the station of G103 in a unit of relaxation time. Using measurements from the footwall of the Chelungpu fault as controlling parameter, the simulation at hanging wall has less value than observation. It suggests a great deal of stress release resulting from the geological material loosen and easy to be deformed at postseismic stage. In addition, when the plate continue moves from southeast to northwest, the regional concentrative stress still focus on the Chi-Chi area. Thus the reason, we have got a larger variation between observation and simulation in this vincity. Whenever the postseismic displacement pattern stop, the stress accumulation will act on again with time spin increases. With the observation and simulation, it is found the relaxation time of asthenosphere of the region is about 4.2-12.5years.
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