基于Sentinel-1A数据反演漾濞MS6.4地震的同震形变场及断层几何参数

2021年5月21日晚21时48分,云南省大理州漾濞县(震中:25.67°N,99.87°E)发生M_S6.4地震,震源深度8 km。为快速获得此次地震同震形变场及断层几何参数,研究该次地震的发震构造等,文章基于震前、震后的sentinel-1A卫星升降轨SAR数据进行二轨法差分雷达干涉测量(DInSAR),并基于Okada弹性半空间位错模型反演断层几何参数。研究结果如下:(1)此次地震造成的同震形变场长约19 km,宽约20 km;(2)升轨雷达视线向最大形变约为8.2 cm,降轨雷达视线向最大形变约为8.7 cm;(3)地震断层走向为313.7°,倾角为87°,滑动角为175°,为右旋走滑型断层,最大滑动量为0.79 m,反演得出的地震矩为1.48×10~(18) N·m,矩震级为M_W6.1。在川滇块体向南挤出的构造背景下,块体西边界的维西—乔后断裂、红河断裂发生右旋走滑,本次地震便是维西—乔后断裂南段分支断裂右旋走滑活动的体现。

Inversion of the coseismic deformation field and fault geometric parameters of the Yangbi MS6.4 earthquake based on Sentinel-1A data

At 21: 48 on May 21, 2021, an M_S6.4 earthquake occurred in Yangbi County, Dali Prefecture, Yunnan Province (25.67°N, 99.87°E), with a focal depth of 8 km. In this paper, the coseismic deformation field and the seismogenic structure of theM_S6.4 earthquake were analyzed with the two-pass DInSAR technique and the ascending and descending SAR data from sentinel-1A satellite before and after the earthquake, and geometric parameters of the fault were inverted based on the Okada elastic dislocation model. The research results are as follows: (1) The coseismic deformation field caused by the earthquake is about 19 km long and 20 km wide; (2) The maximum deformation along ascending radar line of sight (LOS) and descending radar LOS are about 8.2 cm and 8.7 cm, respectively; (3) The strike, dip and rake of the earthquake fault is 313.7°, 87° and 175°, respectively. The fault slip is right-lateral strike-slip with a maximum value of 0.79 m. The seismic moment obtained by inversion is 1.48×10¹⁸ N·m, and the moment magnitude is M_W6.1. Under the tectonic background of southward extrusion of Sichuan-Yunnan block, right-lateral strike-slip occurred along the Weixi-Qiaohou fault and the Honghe fault on the west boundary of the block. This earthquake is the reflection of right-lateral strike-slip activity along the south branch of Weixi-Qiaohou fault.