菲律宾棉兰老岛2019年4次M_(W)>6.0地震断层运动模型及库仑应力传输研究

Research of the Coseismic Faulting Models and Coulomb Stress Transfer of the Four M_(W)>6.0 Earthquakes in Mindanao Island,Philippines in 2019

基于雷达干涉测量技术,利用ALOS-2、Sentinel-1卫星升降轨雷达影像,获得2019-10~12发生在菲律宾棉兰老岛的4次M_(W)>6.0地震的同震形变场,并以此形变结果为约束,反演得到4次地震的断层运动模型。综合分析发现,此次地震序列由3条断裂的破裂引起,其中2019-10-16和2019-10-31的2次地震为同一发震断裂,2019-10-31地震断层破裂区域位于2019-10-16地震断层破裂的东北延伸段,最大滑动量约为1.1 m,约为2019-10-16地震最大滑动量的2倍。2019-10-29地震由一条独立断层破裂引起,断层最大滑动量约为2.0 m。2019-12-15地震由一条东北向倾斜断层破裂引起,断层最大滑动量约为3.0 m。此外,2019-10-16地震引起2019-10-29地震显著滑动区明显的正向库仑应力传输;而2019-10-29地震显著增加了2019-10-31地震震源区域的库仑应力;前3次地震对2019-12-15地震孕震断层的库仑应力传输总和为负值,说明静态库仑应力传输可能不是此次地震触发的主要诱因。

Using ALOS-2 and Sentinel-1 satellites SAR images based on the InSAR technology,we extract the coseismic surface deformation fields of the four M_(W)>6.0 earthquakes that occurred between October to December of 2019 in Mindanao Island,Philippines.Then,we use the InSAR data to estimate the coseismic faulting model of these four earthquakes.The inversion result shows that the rupture of three individual faults are responsible for these four earthquakes.The dextral strike rupture of two adjacent segments of the same southeast dipping fault caused the two earthquakes occurred on 2019-10-16 and 2019-10-31,respectively.The maximum slip magnitude of the 2019-10-31 earthquake is about 1.1 m,which is two times of that of the 2019-10-16 earthquake.Another fault for the earthquake occurred on 2019-10-29,and the maximum slip magnitude is about 2.0 m.An additional fault characterized by predominant sinistral strike slip is the seismogenic fault of the 2019-12-15 earthquake,with a maximum slip magnitude of about 3.0 m.The calculation of the Coulomb failure stress(CFS)change indicates that the 2019-10-16 earthquake has caused significant positive CFS change in the high-slip area of the 2019-10-29 earthquake.Moreover,the 2019-10-29 earthquake also increased the CFS in the hypocenter area of the 2019-10-31 earthquake.Finally,the cumulated CFS change on the seismogenic fault of the 2019-12-15 earthquake due to the previous three earthquakes is less than zero,which suggests that the static CFS changes may be not the main triggering factor of the 2019-12-15 earthquake.