2020年伽师M_(s)6.4地震InSAR同震形变与滑动分布特征分析

Analysis on InSAR Co-seismic Deformation and Slip Distribution Characteristics of 2020 Jiashi M_(s)6.4 Earthquake

利用Sentinel-1A升轨和降轨数据,基于D-InSAR技术,获取2020年1月19日伽师M_(s)6.4地震同震形变场,并结合其他研究机构给出的震源机制解参数和已有研究成果,反演得到伽师地震的发震断层几何特征和滑动分布。研究结果表明,伽师地震同震形变在地表有明显差异;升轨同震形变在卫星视线方向北侧抬升55 mm,南侧下降42 mm;降轨同震形变在卫星视线方面北侧抬升63 mm,南侧下降23 mm。通过反演得到发震断层走向为275°,倾角为20°,地震滑动主要分布在地下5 km处,最大滑动量约为0.32 m,平均滑动角为89.3°,累积地震矩为1.46×10^(18) N·m,合矩震级M_(w)6.1,发震构造为具有少量走滑性质的逆冲断裂。从发震构造特征、同震滑动分布推测,伽师地震发震构造是柯坪塔格褶皱带滑脱面以上沉积盖层内的逆冲断裂,支持了柯坪推覆体的薄皮构造模型观点。

By using Sentinel-1A ascending and descending data with the method of D-InSAR, the co-seismic deformation of Jiashi earthquake occuring on 19th January 2020 was obtained. Combing with the focal mechanisms given by other research agencies, the geometric characteristics and slip distribution of seismic fault was inversed. Our study result shows that, the co-seismic deformation of Jiashi earthquake has obvious difference on surface: co-seismic deformation of the ascending orbit lifts 55 mm in the north and 42 mm in the south in LOS direction, co-seismic deformation of the descending orbit lifts 63 mm in the north and 23 mm in the south in LOS direction. Inversion result shows that seismic fault strike angle is 275°, dip angle is 20°, seismic slip is mainly distributed at 5 km underground, maximum slip is about 0.32 m, the average slip angle is 89.3°, the cumulative co-seismic moment is 1.46×10^(18) N·m, which is equal to the moment magnitude of M6.1, the seismogenic structure is a thrust fault with minor strike slip property. According to the characteristics of seismogenic structure and co-seismic slip distribution, our result indicates that the Jiashi earthquake seismogenic structure is a thrust fault in the sedimentary mantle above the detachment surface of kepingtag fold belt, and supports the thin skinned structural model of Keping nappe.