Surface deformation induced by the 2016 Meinong earthquake and its implications to active folds

Abstract

We present 230 field observations on the location, trending, and displacement vectors of the coseismic surface cracks induced by the 2016 Meinong earthquake in the Guanmiao area, SW Taiwan. Coseismic surface cracks trends from the north to northeast. The coseismic deformed region moved toward the W-WNW. In Guanmiao town, surface cracks were mainly distributed on both limbs of the Guanmiao syncline. The preseismic deformation was also observed along the axial trace of the Guanmiao syncline. These results give clues to high structural activities in SW Taiwan. We argue that Guanmiao syncline is an active fold with both coseismic activity and interseismic creeping, which induced nonnegligible micro-geohazards because of the continual loss. We report a new case of the normal bending-moment fault, the Luosianliao fault, which locates between the Guanmiao syncline and Chungchou anticline. However, the linkage between the shallow Luosianliao fault and the deep-seated causative fault of Guanmiao aftershocks are not known yet. We demonstrate the kinematic process of coseismic surface deformation and argue that the bending-moment fault could provide an opportunity to understand the recurrence interval of folding. The mechanism of earthquake-induced folding amplification through high fluid-pressure rocks may play a critical role in assessing earthquake hazard risks in regions with similar geology to SW Taiwan.