INSAR AND GPS EARTHQUAKE SOURCE PARAMETER INVERSION FOR THE 2016 Mw6.4 MEINONG, TAIWAN EARTHQUAKE

On February 6, 2016, an M_w6.4 earthquake struck the Meinong District of Kaohsiung city in Taiwan, China. Various researches have been conducted on the earthquake. Most of these researches are based on seismic data and no consensus has been reached on the fault structure and focal parameters yet. Surface displacement obtained by interferometric synthetic aperture radar (InSAR) is widely used in earthquake studies because of its high resolution and accuracy with large and continuous coverage. Therefore, this study selects InSAR and GPS data to investigate the focal mechanism and slip distribution of the 2016 Meinong earthquake. Using the dual-track differential InSAR (D-InSAR) technology, we extract the coseismic deformation field of this earthquake with SAR data (both the ascending and descending) from satellite ALOS2 and the ascending data from satellite Sentinal-1A. The results show that the maximum deformation occurs in the west of the epicenter, with an uplift around 11.2 cm.

The uniform dislocation model and multiple peak particle swarm optimization (MPSO) algorithm are employed to determine the fault geometry parameters of this earthquake based on the InSAR and GPS data. The results show that the rupture is a reverse fault with sinistral strike-slip with the average slip angle of 51.5°. The seismic source is at 22.920°N, 120.420°E, and a depth of 12 km. The rupture plane is about 15 km long with a strike angle of 307° and a dip angle of 16.5°. The optimal dip angle (15.7°), weighting ratio (18:1) between GPS and InSAR and the smoothing factor (0.06) obtained by the grid iteration method together with the non-uniform model and the non-negative least squares method are used to obtain the detailed slip distribution. The results show that the maximum value of dip slip and strike slip are 51.7 cm and 55.3 cm, respectively. The moment magnitude of the non-uniform model is M_w6.38, slightly smaller than the result of GCMT (M_w6.4). The comparison between our research and previous research and the analysis of the regional faults indicate that a single fault geometry is more reasonable and it can fit both the GPS and InSAR data well. We also find that the ruptured fault is a blind fault located in the area among Zouchen fault and Chishan fault with an ES-WN strike and dipping toward ES. So we believe this fault should have some relation with the 2010 M_w6.3 Jiashian earthquake.