2022年9月5日泸定M_(S)6.8地震对周围地表和后续地震的影响及与背景应力的关系

Influence of the Luding,Sichuan M_(S)6.8 Earthquake on Sep.5,2022 on the Surrounding Region and Subsequent Earthquakes and Its Geodynamics Background

为确定2022年9月5日四川泸定M_(S)6.8地震的破裂方式及对周围区域的影响,首先收集整理各机构和学者的震源机制解,给出可信的震源机制中心解,然后使用地震破裂模型计算了同震位移场和应变场,以及泸定M_(S)6.8地震对M_(S)5.0地震的库仑破裂应力变化,分析其对后续地震的影响。结果显示:震源机制中心解节面I走向为163.55°,倾角为79.39°,滑动角为-0.11°;节面Ⅱ走向为253.57°,倾角为89.89°,滑动角为-169.39°,是一次走滑型地震。位移场和面应变都呈四象限分布,且位移以水平位移为主,符合走滑型地震产生的位移场特征;M_(S)6.8级地震在10月22日M_(S)5.0地震的破裂面和滑动方向上产生的库仑破裂应力变化为0.168MPa,表明对后者的发生有触发作用;将当地的应力场投影到M_(S)6.8地震的断层面上,得到相对剪应力和正应力分别为0.772和0.225,表明本次M_(S)6.8地震是在当地应力背景下,应变能积累后的一次正常释放。

In order to determine the rupture mode of the Luding,Sichuan M_(S)6.8 Earthquake on Sep.5,2022 and its impact on the surrounding areas of the epicenter,we collected and sorted out the focal mechanism solutions of various institutions and scholars,and obtained the central focal mechanism solution.Then,based on the rupture model of the earthquake,we calculated the co-seismic displacement field and strain field,and the Coulomb Failure Stress(CFS)change of the Luding M_(S)6.8Earthquake on the M_(S)5.0 Earthquake to analyze its impact on subsequent earthquakes.As the results show,the M_(S)6.8Earthquake is of a strike-slip type,with the strike,the dip angle,and the slip angle of nodal plane I of central focal mechanism being 163.55°,79.39°and-0.11°respectively,and those of node II being 253.57°,89.89°and-169.39°respectively.Both the displacement field and the areal strain show a pattern of four quadrant distribution,with the displacement being mainly horizontal,which conforms to the characteristics of displacement field generated by strike-slip earthquakes.The CFS change generated by the Luding M_(S)6.8 Earthquake on Sep.5,2012 projected on the fault plane and slip direction of the Luding M_(S)5.0earthquake on Oct.22,2012 is 0.168MPa,indicating the triggering effect on the occurrence of the latter.By projecting the local stress filed on the fault plane of the Luding M_(S)6.8 Earthquake,it is found that the relative shear and normal stress are0.772 and 0.225 respectively,which indicates that the M_(S)6.8 Earthquake is a normal strain energy release under the action of the local stress.