Abstract
On 4 March 2010, an inland M(subscript w) 6.3 earthquake occurred near the town of Jiasian in Kaohsiung County, Taiwan causing large ground shaking and extensive damage. In this study, we integrate the records from the Central Weather Bureau Seismic Network (CWBSN) and Taiwan Strong Motion Instrumentation Program (TSMIP) to obtain the relocated earthquake sequence and its first-motion focal mechanisms. This dataset offers us precise and reliable results which suggest a focal depth of 23 km and a possible fault plane of strike 313°, dip 41°, and rake 42° for the Jiasian earthquake. This fault plane significantly differs from the N-S striking Chaochou Fault (CCF) as well as the principal trend of Taiwan orogenic belt, and should be an undiscovered fault in southern Taiwan. The relocated Jiasian earthquake sequence initiating from the 23-km-deep mainshock and terminating at around 10 km in depth also indicates it is a blind fault. Peak ground acceleration (PGA) and peak ground velocity (PGV) recorded by the TSMIP stations reveal a distinct NW-SE-shape pattern from the epicenter area toward the Chiayi region, likely due to the directivity and site effects. Such phenomena should be considered for future regional hazard assessments.
Highlights
On 4 March 2010, an inland shallow earthquake (ML = 6.4 and Mw = 6.3) near the town of Jiasian in Kaohsiung County, Taiwan, was reported by the Central Weather Bureau (CWB) rapid reporting system (Wu et al 1997, 2002) and named the “2010 Jiasian earthquake” (Fig. 1)
A total of 362 polarities collected from Central Weather Bureau Seismic Network (CWBSN) and Taiwan Strong Motion Instrumentation Program (TSMIP) provided us a much denser coverage to better constrain the fault plane
The maximum and minimum principal stress axes (σ1 and σ3) are orientated in the azimuth of 256° and 144° with plunges of 13° and 58°, respectively. When we compared these results with results from Global Centroid Moment Tensor (GCMT), Broadband Array in Taiwan for Seismology (BATS), and CWB, they are roughly consistent (Fig. 1)
Summary
On 4 March 2010, an inland shallow earthquake (ML = 6.4 and Mw = 6.3) near the town of Jiasian in Kaohsiung County, Taiwan, was reported by the Central Weather Bureau (CWB) rapid reporting system (Wu et al 1997, 2002) and named the “2010 Jiasian earthquake” (Fig. 1). It produced widespread strong ground shaking in southern Taiwan. In case that the NW-SE striking plane is the causative fault, its strike direction would be significantly different from that of the CCF and the principle structural orientation of the Taiwan orogenic belt at N20°E, which would imply the existence of a yet undiscovered structure
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