Sentinel-1A及ALOS2数据约束下的阿克陶地震震源参数反演及发震构造研究

2016年11月25日，在新疆阿克陶县发生了M_W6.6地震.本文利用Sentinel-1A宽幅数据和ALOS2精细数据获得了同震形变场，干涉形变场沿木吉断裂展布，显示本次地震破裂长度可达70 km，在地表形成两个形变中心，且震中东部形变场条纹密集而西部稀疏、影响范围广，跨断层剖面显示视线向最大形变量可达12 cm.利用一种结合先验知识的多视角最小二乘迭代分解法求解出地表的三维形变场，结果显示震中东部形变中心垂向向下运动最大可达20 cm，木吉断裂南侧西向运动可达10 cm，断层表现为右旋走滑兼具正断作用.采用前向模拟的方法确定二段式分段断层模型能够较好地恢复观测形变场，进而以InSAR观测数据为约束，基于弹性半空间形变模型采用两段非均匀断层滑动模型来反演断层面上的精细滑动值.反演结果显示本次地震可能为两次地震事件，发生在断层西段的第一次事件以右旋走滑为主，走向103°，倾角76°，滑动角-167°，震源深度10.1 km，累计地震矩为7.2×10¹⁸N·M；东段的第二次事件为右旋走滑兼具正断作用，走向109°，倾角略缓约55°，滑动角-160°，震源深度5.3 km，累计地震矩7.76×10¹⁸N·M.本次地震是一次发生在公格尔拉张系的拉张环境下的构造地震.

Study of the D-InSAR deformation field and seismotectonics of the Aketao MW6.6 earthquake on November 25, 2016 constrained by Sentinel-1A and ALOS2

On November 25, 2016, a M_W6.6 earthquake occurred in Aketao County, Xinjiang. In this paper, the coseismic deformation field of the earthquake is obtained by using Sentinel-1A TOPSAR data and ALOS2 fine mode data. The interferogram deformation field is distributed along the Muji fault, showing that the earthquake rupture length can reach 70 km, and two deformation centers are formed on the surface. The deformation field eastern to the epicentral is fringe-dense,but the western part is sparsely and has a wide influence range. The cross-sectional profile shows that the maximum deformation of Line of Sight can reach 12 cm. The three-dimensional deformation field of the surface is solved by a multi-angle least square iterative decomposition method constrainted by prior knowledge. The results show that the vertical downward movement of the epicentral eastern deformation center can reach up to 20 cm, and the westward movement of the south side of the Muji fault can reach 10 cm, which shows that the fault main motion characteristics is dextral strike, and have normal slip component. Firstly, the method of forward simulation is used to determine source parameter of the two-segment fault model to recover the observed deformation field, and then the InSAR observation data is used as the constraint to invert the fine slip distribution on the fault plane. The result shows that the earthquake consists of two events. The first event is dominated by dextral strike and occurred on the western section with the striking 103°, the inclination is 76°, the rake angle is -167°, the focal depth is 10.1 km, the cumulative seismic moment is 7.2×10¹⁸N·M. The second event occurred on the eastern section with the striking 109°, the dip 55°, the rake -160°, the focal depth 5.3 km and the cumulative seismic moment 7.76×10¹⁸N·M, but which has normal slip component. It is a tectonic earthquake occurred at Gongur Shan extensional system.