关键词: 甲仙地震, 震源参数反演, InSAR, 地震触发, 静态库伦应力

Abstract: InSAR and GPS have great advantages in seismic research. InSAR can quickly obtain continuous co-seismic deformation observation in a wide range, while GPS has high accuracy and can quickly obtain stable measurement. With the increase of SAR satellites and the shortening of the return period, it is more powerful to study the seismic triggering relationship and stress effects by using InSAR and GPS jointly. On March 4, 2010, and February 6, 2016, two earthquakes with M_w>6.0 occurred successively in southwestern Taiwan, which are called Jiashian earthquake and Meinong earthquake, respectively. Those are two of the three destructive earthquakes that have occurred in the southwestern plain of Taiwan in the last 200 years (the other was the 1946 M 6.1 Hsinhua earthquake). The time and space intervals between Jiashian and Meinong earthquakes are very small. The study of the relationship between them can not only explore the underground structure of the two events but also further understand the triggering relationship between strong earthquakes. In addition, the effect of the surrounding faults after the two events and which faults have high seismic risk are also worth discussing. As no scholar has deeply studied the relationship between the two events and the effect of the surrounding faults, we used the GPS and InSAR coseismic deformation obtained from ALOS to invert the slip distribution model of the Jiashian earthquake. Based on the static Coulomb stress model, the relationship between Jiashian and Meinong earthquake is analyzed. Seven faults in southwestern Taiwan have been constructed and the stress change models of them have been obtained. We analyzed the high earthquake risk area in southwestern Taiwan based on these stress change models. Fault model obtained by InSAR and GPS inversion shows that the fault structures of Jiashian and Meinong events are very similar, both of which are thrust faults with certain strike-slip. The major slip area of the Jiashian event is between 12~16 km which is slightly deep than that of the Meinong event. The maximum slip of the Jiashian event is 0.61 m at about 14 km depth. The moment of the Jiashian event we obtained by linear inversion is 2.27×10¹⁸ Nm corresponding to M_w 6.20 which is consistent with the results of USGS (M_w 6.21) and GCMT (M_w 6.3). After Jiashian earthquake, the stress on the causative fault of Meinong event increased greatly, the maximum increment reached 4.0 MPa, and the area of stress increase accounted for about 74% of the total area of the inferred fault. This shows that the Jiashian earthquake has a very obvious acceleration effect on the Meinong earthquake. However, after the Meinong event, the stress of the causative fault of the Jiashian event increased less, and the average increment is only 0.03 MPa. Under the combined effect of the Jiashian and Meinong events, the Zouchen and Hsinhua faults on the west of the Jiashian earthquake have obviously stress accumulated. We believe that Zuochen and Hsinhua faults in southwestern Taiwan are of high risk after Jiashian and Meinong earthquakes, which deserve continuous attention and further study.

Key words: the Jiashian earthquake, inversion of seismic source parameters, InSAR, earthquake triggering, static Coulomb stress