2020-07-23西藏尼玛M_(w)6.3地震震源参数InSAR反演与发震构造研究

Source Parameter Inversion and Seismogenic Tectonic of the Nyima M_(w)6.3 Earthquake in Tibet on July 23, 2020 Based on InSAR

针对2020-07-23西藏尼玛M_(w)6.3地震发震构造的复杂性(无明显地表破裂、发震断层倾向存在争议等),利用哨兵-1A升、降轨影像数据获取此次地震的同震形变场,并以此为约束通过设置两组可能性断层滑动模型及结合区域余震分布和地质构造背景,探讨此次地震发震断层的活动方式,在此基础上进一步反演获得断层面滑动分布特征。结果表明,此次地震发震断层为依布茶卡地堑东侧NWW向正断层,断层走向为207°,倾角为33.1°,平均滑动角为-89.27°,以正断倾滑为主;地震破裂主要集中在沿断层面5.4~9.3 km深处(未破裂至地表),最大滑动量约1.7 m,矩震级为6.3级。此次地震的发生是青藏地块现今构造运动变形的结果。

Aiming at the complexity of seismogenic structure of the Nyima M_(w)6.3 earthquake in Tibet on July 23, 2020(no obvious surface rupture, the tendency of seismogenic fault is controversial), we obtain the coseismic deformation fields based on the ascending and descending orbit Sentinel-1 A images. As a constraint, the seismogenic fault activity mode of this earthquake is discussed by setting two groups of possible fault slip models and combining with regional aftershock distribution and geological structure background. On this basis, the slip distribution characteristics of fault plane are further obtained. The results show that the seismogenic fault is a normal fault that dips to NWW located on the east side of the Yibug Caka graben, with a strike angle of 207°, dip angle of 33.1°, average slip angle of-89.27°, and dominated by dip slipping. The earthquake rupture is mainly concentrated at the depth of 5.4-9.3 km along the fault plane(unruptured to the surface), the maximum slip is approximately 1.7 m, and the moment magnitude is 6.3. The occurrence of this earthquake is the result of the current tectonic movement and deformation of the Qinghai-Tibet block.