Reexamining the source parameters of the 2010 ML 6.4 JiaSian (Taiwan) earthquake using the inversion of teleseismic P-waves

A moderate-sized earthquake (ML = 6.4), named the 2010 JiaSian earthquake, occurred in southern Taiwan on March 4, 2010. Reports from several institutes indicated that the JiaSian earthquake had focal depths of 18–28 km and ruptures with a thrust mechanism. However, modeling of teleseismic P-waves in previously reported source parameters revealed significant differences between the observed and synthetic P-waves. Therefore, this study reexamined the source parameters of the 2010 JiaSian earthquake using a teleseismic P-wave inversion method. The inversion showed that the earthquake had a depth of 22 km, a best double couple of 304°/28°/48° and 170°/70°/110° (strike/dip/rake), and a seismic moment of 2.31 × 1018 N m (MW = 6.2). Rupture directivity analysis also suggested that the earthquake was a unilateral faulting event on the fault plane of 304°/28°/48°. The average source duration and the rupture length were ∼5.2 s and ∼19.4 km, respectively. The optimal rupture direction, measured counterclockwise from the strike on the fault plane, was 347°, which was projected onto the surface to correspond to the northwestward rupture, consistent with the aftershock distribution. The analysis also suggested a high rupture velocity during faulting, probably approximate to the crustal S-wave velocity, which may have resulted in a low static stress drop and caused the differences in PGA distribution along the direction of earthquake rupture. The dip angles of the fault plane estimated from the initial and centroid depths showed the initial rupture at a lower dip-angle plane and the later rupture at a higher dip-angle one.