2017年精河MS6.6地震邻区构造应力场特征与发震断层性质的厘定

2017年8月9日新疆精河发生M_S6.6地震，深入了解该地震的构造应力背景及其所破裂断层的活动特性对理解其孕震过程及震后的地震危险性估计十分重要.本研究自GCMT目录收集了2017年8月9日新疆精河M_S6.6地震震中及其邻区的253个震源机制解，应用MSATSI软件反演了该地震及其邻区的应力场.反演结果显示，西北区域应力场的最大主压应力轴的方位从西到东呈现出NNW-NS-NNE的渐变过程，东南区域应力场最大主压应力轴的方位稳定于NNE向，倾角都较小；最大主张应力轴都基本沿东西向，倾角相对较大；西北区域较大的R值显示出区域应力场主要受近NS向水平挤压作用，中部挤压分量相对较大，西部和东部挤压分量相对较小.根据所反演的区域构造应力场，结合发震的库松木契克山前断裂的地质调查参数，估算该断裂的理论滑动角为137.7°，误差为21.3°，验证了地质上得到的库松木契克山前断裂的逆冲兼右旋走滑性质.判断该断裂滑动性质的另一种方法是通过发生在该断裂上地震的震源机制验证.本研究首先计算了发生在库松木契克山前断裂不同机构给出的震源机制节面在所反演的局部应力场作用下的理论滑动角，发现理论滑动角与实际地震震源机制滑动角相差很小，验证了反演的局部应力场的正确性；而后计算了局部应力场作用下的库松木契克山前断裂上的理论震源机制与实际发生地震震源机制的三维空间旋转角，发现两者在给定的误差范围内是一致的.本研究自地球物理角度确证了库松木契克山前断裂的滑动性质，为该地区的地震孕育环境、地震活动性和地球动力学研究提供了基础.

The tectonic stress field adjacent to the source of the 2017 Jinghe MS6.6 earthquake and slip property of its seismogenic fault

The M_S6.6 earthquake occurred in Jinghe County, Xinjiang on August 9, 2017. It is very important to study the background tectonic stress of the earthquake and the active characteristics of the ruptured fault in order to understand its seismogenic process and estimate the subsequent seismic risk of the earthquake. Based on the 253 focal mechanism solutions around the Jinghe M_S6.6 earthquake on August 9, 2017 collected from GCMT, this study carries out the inversion of the stress field in the source region by using MSATSI software. The inversion results of north-west show that the azimuths of the maximum principal compressive stress of the regional stress field present the gradual process of NNW-NS-NNE from west to east, and The position of the maximum principal compressive stress axis in the southeast region are stable to NNE direction, with a small dip angle. And the minimum principal compressive stress axis are mainly in EW direction with a relatively large dip angle. The larger R values of north-west region indicate that the regional stress field is mainly subjected to horizontal extrusion in NS directions. The compressive components in the central part are relatively large, while they are relatively small in the southern and eastern parts. Based on the inversion results of the regional tectonic stress field and the geological survey parameters of the seismogenic fault (Kusongmuxieke mountain front fault), the theoretical slip angle of the fault is estimated to be of 137.7° with an error of 21.3°. The results show that the Kusongmuxieke mountain front fault has a thrust and right-lateral strike-slip property, which is consistent with the geological survey. Another way to judge the slip feature of the fault is the focal mechanism of the earthquake that occurred on it. Firstly, we calculate the theoretical slip angles of the focal mechanisms given by different institutions which occurred on the Kusongmuxieke mountain front fault under the local stress field. We found that the theoretical slip angle is little different from that of the actual seismic focal mechanism. Therefore, the correctness of the local stress field is verified. After that we calculate the three-dimensional rotation angle between the above theoretical focal mechanism and the actual seismic focal mechanism. The results show that the two are consistent within a given error range. From the perspective of geophysics, the slip properties of Kusongmuxieke mountain front fault are confirmed, which provides the foundation for the research on the seismogenic environment, seismicity and geodynamics in the area.