A study of the seismogenic process beneath the south-western foothills in Taiwan in relation with the 2010 Jiasian earthquake

Abstract

A moderate earthquake occurred near the town of Jiasian in Kaohsiung County, Taiwan, at 8:18AM (local time) on 4 March 2010. The epicenter was located about 60km northeast of Kaohsiung City. About 70 aftershocks occurred during the same day. In this study, we invert a 3-D velocity structure beneath the southwestern part of Taiwan. Furthermore, we accurately determine the locations, the focal mechanisms, and the regional stress tensor from the inverted 3-D velocity model. According to the results, we can conclude: (1) a low Vp anomaly zone with a high Vp/Vs ratio in the southwestern part of the research area may have been caused by the subducting oceanic lithosphere; (2) a high Vp anomaly zone with low Vp/Vs ratio in the northeastern part of the research area demonstrates that there is an intervening continental sliver; (3) based upon the inverted 3-D velocity model and the relocated seismicity, we suppose that there might be a NW–SE trending blind fault which dips to the north; (4) according to the results of the focal mechanisms of the Jiasian earthquake sequence and the regional stress tensor inversion, we can surmise that the possible blind fault may be a thrust fault with left-lateral characteristic; and, (5) based upon the different tectonic process in this area, we can conclude that the Chishan Transfer Fault Zone leads to a possible oblique slip fault locks and exhibit high seismic potential which caused the Jiasian earthquake sequence.