2018年9月4日新疆伽师MS5.5地震序列及发震构造讨论

Discussion on Earthquake Sequence and Seismogenic Structure for the Jiashi MS5.5 Earthquake on September 4,2018,Xinjiang

摘要:

2018年9月4日新疆伽师发生M_S5.5地震，震中处于塔里木地块西北缘，位于1997~1998年伽师强震群震区内。此次伽师地震前发生了M_S4.7前震，截至9月30日最大余震震级为M_S4.6（M_L5.0），初步判定为前-主-余型地震序列。序列精定位结果显示，余震沿近NE向展布，主震震源深度与1997~1998年伽师强震主震基本一致，发震断层陡立。本文从区域的构造环境、地震震源机制解和余震分布特征等方面分析认为，地震发生在伽师隐伏断裂东南端部，为1997~1998年伽师强震群震区的一次新的构造活动。序列参数、视应力等计算结果显示，伽师M_S5.5地震的预测最大余震震级与最大余震震级M_S4.6接近，表明序列最大余震已经发生。

Abstract:

The Jiashi M_S5.5 earthquake occurred on September 4,2018 in Xinjiang Uygur Autonomous Region,the epicenter is located in the northwestern margin of the Tarim block,in the seismic area of 1997-1998 Jiashi strong earthquake swarm. The Jiashi earthquake has M_S4.7 foreshock,the largest aftershock magnitude M4.6,preliminarily determined as a pre-main-aftershock sequence. The precise positioning results show that the aftershocks are distributed along the NE direction,and the depth of the main shock is basically the same as that of the 1997-1998 Jiashi strong earthquakes. The seismogenic fault rises steeply. In this paper,the seismogenic process of this earthquake is analyzed from the aspects of regional tectonic environment,focal mechanism solution and aftershock distribution. It is considered that the earthquake occurred on the southeastern margin of Jiashi concealed fault,which is a new tectonic activity in the Jiashi strong earthquake swarm area from 1997 to 1998. The calculation results of sequence parameters and apparent stress show that strong earthquakes in the Jiashi earthquake area are unlikely to occur in the near future.