| Summary: | 碩士 === 國立中央大學 === 地球物理研究所 === 100 === The load-unload response ratio (LURR) has recently shown promising performance for earthquake forecasting in China, Japan and California. From the viewpoint of fracture mechanics, the preparation process of an earthquake is basically the damage process of the hypocentral media. LURR has been proposed as a measure characterizing the evolution of the damage process of the crust and is calculated from the seismicity variations during loading cycles respectively during the unloading cycles. The loading-unloading cycles are performed by the stress changes induced by the Earth tides acting upon some specific fault plane. In this study, the LURR has been used to detect the precursory damaging process before six large earthquakes, 1998 Rueili, 1999 Chi-Chi, 1999 Chiayi, 2000 Hualien, 2006 Peinan, 2009 Mingjian and 2010 Jiashian, Taiwan, earthquakes. LURR is defined as Y=X+/X-, where X+ and X- are the response rates during loading and unloading cycles, respectively. When a seismogenic system is relatively stable Y ~ 1. To the contrary, when the system is in an unstable state Y > 1. The response rates can be determined from either earthquake numbers, the Benioff strain, the size (length or area) scales of the focal zone or the seismic energy. Using the LURR index as presented in this study, the epicenters of these main shocks was found to exhibit anomalous high LURR values before these two events. We therefore suggest that the LURR approach could be helpful in detecting the anomalous seismicity and catastrophic damaging process of the crust.
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