Pre-seismic strain anomalies and coseismic deformation of Meinong earthquake from continuous GPS

Abstract

High strain accumulation across the fold-and-thrust belt in SW Taiwan are revealed by the Continuous GPS (cGPS) from 2007 - 2015. This high strain is generally accommodated by the major active structures in fold-and-thrust belt of western Foothills. In addition, the plastic deformation of mudstone in the Gutingkeng formation might play a crucial role for aseismic creeping. Furthermore, the distributed right-lateral shear zone, fault-related folding and aseismic creeping are also dominated from Lungchuan fault and Chishan fault to the north of Kaohsiung area. Based on distribution of coseismic uplift across the Lungchuan fault to the Tainan tableland, a clear evidence of multiple fault slips was triggered by the 2016 Mw 6.4 Meinong earthquake at ~15 km. The surface coseismic deformation is mainly controlled by a fault-related folding structures connected to the shallow décollement around 5 - 10 km depth, in which the moderate earthquakes locate in mid-crust could trigger slip along the weak décollement. The pre-seismic baseline variation of cGPS is observed in 8 baselines near the epicenter of the Meinong earthquake. The rate-slow-down anomalies of these baseline variation could be considered as a possible precursor of the Meinong earthquake.