2021年5月21日云南漾濞M_(S)6.4地震序列双差重定位及其构造意义  

DOUBLE-DIFFERENCE RELOCATION OF YUNNAN YANGBI M_(S)6.4 EARTHQUAKE SEQUENCE ON MAY 21,2021 AND TECTONIC IMPLICATIONS

作　　者：许永强 雷建设 胡晓辉 XU Yong-qiang;LEI Jian-she;HU Xiao-hui(School of Coal Engineering,Shanxi Datong University,Datong 037000,China;Key Laboratory of Crustal Dynamics,National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]山西大同大学,煤炭工程学院,大同037000 [2]应急管理部国家自然灾害防治研究院,地壳动力学重点实验室,北京100085 [3]中国科学技术大学,地球和空间科学学院,合肥230026

出　　处：《地震地质》2024年第5期1066-1090,共25页Seismology and Geology

基　　金：青藏高原第2次科学考察项目(2019QZKK0708);应急管理部国家自然灾害防治研究院科技创新团队(2023-JBKY-55);国家自然科学基金(U1939206)。

摘　　要：文中基于2021年5月1日—2022年6月18日中国地震台网中心收集的2021年5月21日云南漾濞M_(S)6.4地震序列的相关数据,利用双差定位法进行了重新定位,得到了2681个精定位地震事件。结果表明,漾濞地震序列的扩展方向为NW-SE向,长约32km,但并非简单的单侧扩展,而是呈西北窄、东南宽的雁列状分布结构特征,且发震优势深度为5~10km。前震有明显的空间迁移特征,且主震南、北两侧的地震活动差异性明显。这些地震在EW向、SN向、垂直向的平均定位误差约为0.47km、0.50km和0.62km,平均均方根走时残差约为0.22s。采用gCAP全波形反演方法获得该地震序列主断裂上M_(S)≥4.0主要地震事件的震源机制解,结果显示出明显的右旋走滑分量。利用基于小地震反演断层面参数的方法,通过拟合获得了发震断层面的参数,发现主断层面走向在126°~137°之间变化,且由北至南走向逐渐增大,倾向SW,倾角为79°~87°,由北至南倾角逐渐变小。结合该区域的构造应力场及前人的近震层析成像结果推测,漾濞地震的发震构造为漾濞县城西南山地区域中NW-SE走向的高倾角走滑断裂系,该断裂系由一条走滑主断层和多条次级斜交小断层组成,且该地区的地震活动可能受区域应力与深部流体作用共同影响。At 21:48 on May 21,2021(Beijing time),the M_(S)6.4 earthquake occurred in western Town(25.700°N,99.880°E),Yangbi County,Dali,Yunnan Province,with a focal depth of 10km(China Earthquake Networks Center).The Yangbi earthquake is a typical type of foreshock-mainshock-aftershock earthquake,which had a significant impact on the local residents and attracted great attention from society.To better understand the seismogenic structure and mechanism of this earthquake,the present study relocates the May 21,2021 Yangbi M_(S)6.4 earthquake sequence,collected from the China Earthquake Networks Center from 2021 to June 18,2022.Finally,2681 precisely located events are obtained through the double-difference relocation algorithm.Our results show that the Yangbi earthquake sequence extended for about 32km,mainly along the NW-SE direction,and it is an overall echelon structure changing from narrow in the northwest to broad in the southeast.The dominant depth of the earthquake sequence is 5-10km.The foreshocks were mainly active in the northern section of this earthquake sequence,with the mainshock being a unilateral rupture.The aftershocks primarily extended in the southeast direction,but the southeast extension process was not simply a unilateral extension.Multiple secondary oblique activity sequences were derived on the west side of the sequence.With the continuous release of stress in the study area,only the main rupture continued to be active in the southeastern section of the sequence in the later stage of activity.Still,the secondary oblique ruptures that evolved was no longer active.The average location errors of these earthquakes are about 0.47km in the east-west direction,about 0.50km in the north-south direction,and 0.62km in the vertical direction,and the average RMS travel-time residual is 0.22s.This study collects broadband digital seismic waveform data of earthquakes with M_(S)≥4.0 on the main fault of the earthquake sequence recorded by regional seismic networks in Yunnan,Sichuan,and other areas from the Intern

关 键 词：漾濞地震 地震序列 双差定位 震源机制解 发震构造 

分 类 号：P315.2[天文地球—地震学]