Active tear faulting in Hsinchu, Taiwan: A potential threat to Taiwan's economy

Two unusual earthquake swarms struck Hsinchu County in northern Taiwan, near the Hsinchu Science and Industrial Park (HSIP), in 2012 and 2014. In this study, we analyze the focal mechanisms and conduct stress inversion for these swarms and three earthquake clusters located between them. Our results show that both swarms were dominated by right-lateral strike-slip events along a prominent lineation in NW direction. These earthquake ruptures may occur along two previously unrecognized tear faults as they were clearly associated with structural bends in the area. In between, NNE-NE-striking, high-angle reverse-faulting events with left-lateral strike-slip motions were dominant. The faults associated with these events may have originated as horse blocks in a strike-slip duplex bounded by the two tear faults that later rotated clockwise, resulting in bookshelf faulting. Our results suggest the Hsinchu Science and Industrial Park could be under threat of these two nearby tear faults. As the Hsinchu Science and Industrial Park creates about 36% of Taiwan's total trade surplus, our findings urge innovative thinking for hazard mitigation in Hsinchu County to reduce the potential impact on Taiwan's economy.