汶川地区区域构造应力场特征及汶川MS8.0地震对周围主要断层面的影响

为剖析2008年汶川M_S8.0地震对后期地震的影响及发震区域构造应力场特征，首先利用2008年5月12日—2013年4月19日汶川地震及其邻区的1660条震源机制解，同时采用同一地震多个震源机制中心解的方法筛去重复地震事件的震源机制解，最终获得911个震源机制解。其次，通过网格搜索法分段反演出区域构造应力场。结果显示:东北区主要受WNW-ESE向的挤压，西南区受W-E向的挤压，中区受WSW-ENE向的挤压。西南到东北主压应力轴方向有所变化，这可能与龙门山地区受到来自印度板块北北东方向的俯冲推挤、四川盆地的阻挡和巴颜喀拉块体东南向挤压的联合作用有关。然后，基于USGS给出的汶川M_S8.0地震的破裂模型，计算出该地震对附近强震的触发关系，结果表明，本次汶川地震对同属龙门山断裂西南端的芦山地震触发作用明显，对位于东昆仑断裂上的玛多地震也有一定的触发作用。最后，计算汶川M_S8.0地震对周围断层的同震库仑应力变化，发现本次地震造成龙门山断裂南北两端、秦岭南缘断裂、鲜水河断裂东南端、东昆仑断裂、白玉断裂的库仑破裂应力增加，龙门山断裂南北两端和秦岭南缘断裂增加最为明显，对分析地震危险性有一定的参考意义。 

Characteristics of regional tectonic stress field in Wenchuan area and the effect of Wenchuan MS8.0 earthquake on surrounding major fault surfaces

To analyze the influence of the 2008 Wenchuan M_S8.0 earthquake on later earthquakes and the characteristics of the tectonic stress field in the seismogenic region, we first used 1660 source mechanism solutions of the Wenchuan earthquake and its neighboring areas from May 12, 2008 to April 19, 2013, and also used the method of sieving the central solution of multiple source mechanism solutions of the same earthquake to remove the source mechanism solutions of repeated seismic events, and finally 911 solutions were obtained. Then, the regional tectonic stress field is inverse-performed by the grid search method. The results show that the northeast zone is mainly squeezed by the WNW-ESE direction, the southwest zone is squeezed by the W-E direction, and the central zone is squeezed by the WSW-ENE direction. There is a change in the direction of the main compressive stress axis from southwest to northeast, which may be related to the combined effect of subduction thrusting from the north-northeast direction of the Indian plate, blocking from the Sichuan basin and southeastward extrusion of the Bayan Kara block in the Longmenshan area. Then, based on the rupture model of the Wenchuan M_S8.0 earthquake given by the USGS, the triggering relationship of this earthquake on nearby strong earthquakes is calculated. The results show that this Wenchuan earthquake has a significant triggering effect on the Lushan earthquake, which also belongs to the southwest end of the Longmenshan fault, and on the Maduo earthquake, which is located on the East Kunlun fault. Finally, the coseismic Coulomb stress changes of the surrounding faults caused by the Wenchuan M_S8.0 earthquake were calculated. It is found that this earthquake caused an increase in Coulomb rupture stress on the north and south ends of the Longmenshan fault, the south edge of the Qinling fault, the southeast end of the Xianshui River fault, the East Kunlun fault, and the Baiyu fault, with the most obvious increase on the north and south ends of the Longmenshan fault and the south edge of the Qinling fault, which is a reference for the analysis of seismic hazards.