Temporal variation of fault slip rate in southern Taiwan by integrating GPS and InSAR observations

Due to the rapid convergence of Philippine Sea Plate toward the continental margin of Eurasian Plate, the southern Taiwan has a high number of 8 active faults published by the Taiwan Central Geological Survey. We inverted the Global Positioning System (GPS) velocity measurements to investigate the slip rates on these faults and how these values could change with time, especially before and after large seismic events. In this study we employed TDEFNODE to first evaluate two fault-slip models before and after the 2016 Mw 6.4 Meinong earthquake within the periods of 2002 to 2016 (model 1) and 2016 to 2018 (model 2). Our results from these two models show that some long-term average fault slip rates were changed with time, such as the Zuozhen, Chishan and Hengchun faults that have values 30.2, 27.0 and 29.7 mm/yr in 2002-2016 and 15.2, 6.6 and 14.2 mm/yr in 2016-2018, respectively. In addition, we focused on the Mw 7.0 and Mw 6.9 2006 Hengchun doublet earthquakes by integrating the Permanent Scattered Interferometric Synthetic Aperture Radar (PS-InSAR) data collected by ALOS from 2007 to 2011 with the GPS velocities for a joint inversion for fault slip model (model 3). The results show that the average long-term slip rates of the Chishan and Hengchun faults are 12.5 and 16.8 mm/yr, respectively, which are significantly lower than the rates of 2002-2016 (model 1). More fault models with different time spans are on the way to affirm these temporal rate changes and explore their implications on earthquake hazard analysis.