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Title:: Study on Focal Mechanism Solution and Stress Field of the 2021 Yangbi,Yunnan M_S6.4 Earthquake Sequence Using P-wave First Motion Data

作者:: 余海琳¹; 万永革¹; 2; 黄少华¹; 崔华伟³; (1.防灾科技学院,河北三河 065201; 2.河北省地震动力学重点实验室,河北三河 065201; 3.山东省地震局,山东济南 250000)

Author(s):: YU Hailin¹; WAN Yongge¹; 2; HUANG Shaohua¹; CUI Huawei³; (1.Institute of Disaster Prevention,Sanhe 065201,Hebei,China)(2.Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,Hebei,China)(3.Shandong Earthquake Agency,Jinan 250000,Shandong,China)

Keywords:: the Yangbi M_S6.4 earthquake; P-wave initial motion; focal mechanism solution; stress field; maximum shear stress

摘要:: 为揭示2021年云南漾濞M_S6.4地震的发震背景及其与区域应力场的关系,搜集5月18日14时28分至6月8日5时53分的地震序列,采用P波初动反演震源机制解的方法,计算得到漾濞地震前后85次M_S≥2.5地震的震源机制解。根据本次地震序列的震源机制解和近10年内滇西北地区地震的震源机制解,利用网格搜索法反演了该区域的应力场,最后模拟了主震的震源机制与区域应力场的关系。结果表明:该区域主压应力方向为近南北向,主张应力轴方向为近东西向。漾濞主震发生在剪应力最大的区域,且剪应力的滑动角与发震节面的滑动角之差较小,说明此次地震是在构造应力场作用下发生在剪应力最大释放节面上。

Abstract:: In order to reveal the seismogenic background of the Yangbi M_S6.4 earthquake in Yunnan Province and its relationship with the surrounding stress field,the dataset of the seismic sequence from 14:28 on May 18 to 5:53 on June 8 is collected.The focal mechanism solutions of 85 earthquakes with M_S≥2.5 before and after the M_S6.4 main shock are calculated by using the method of P-wave initial motion.Then,according to the focal mechanism solution,the stress field in the source region is inverted by using the grid search method.Finally,the focal mechanism of the main shock and the stress field around it are simulated.The results show that the direction of the main compressive stress is near NS direction,and the extensional stress axis is near EW direction.This result is roughly the same as that of the stress field in the mainland of China.Through the simulation of the stress field and focal mechanism,it is found that the main shock basically occurred in the area with the nearly largest shear stress,and the difference between the direction of the shear stress and the slip direction of the mainshock was small,which indicated that by the action of the tectonic stress field,the mainshock occurred on the nodal plane with maximum shear stress releas.