| Summary: | 碩士 === 國立成功大學 === 地球科學系 === 103 === How to determine the magnitude and the hypocenter in few seconds after an earthquake occurring are two of the most important issues in seismic hazard mitigation. Based on the on-site process, we installed two local early warning arrays in Ilan and Tainan City of the newly established Palert EEW network and adopted the waveform stacking method to enhance the coherent part of early arrivals. The MPd method is used to estimate the earthquake magnitude. By modifying the present Pd attenuation relationships, we show that the accuracy (S.D.V. = 0.28) of magnitude estimation for the on-site EEW mode can be siginificantly improved since the sensors of the nearly built Palert network aer installed inside the building.
The earthquake location for EEW purpose is always a tough problem due to the complicated process and long reporting time. Therefore, we developed a new method to determine the hypocenter in a simple-calculating process. Different events will have different ranking list of the triggered stations due to the geographical distribution if the point source is assumed. We divided Taiwan region into many grids. Each grid is the preset hypocenter and has its own station ranking list as the pre-calculate database computed by the velocity model and 3-D ray tracing method. When an earthquake occurs, we use the real station ranking list to compare the database, and find the least difference grid as the hypocenter. Our results show comparable or better performing than the current operating rapid reporting and EEW systems in Taiwan.
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