2021年青海玛多M_(S)7.4地震发震构造及早期余震传播特征  

The seismogenic structure and early aftershock propagation characteristics of the 2021 Qinghai Madoi M_(S)7.4 earthquake

作　　者：邱镛康 许才军[1,3,4] 肖卓辉 林学楷 张栓 QIU YongKang;XU CaiJun;XIAO ZhuoHui;LIN XueKai;ZHANG Shuan(School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China;Guangzhou Urban Planning Design Survey Research Institute,Guangzhou 510060,China;Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan 430079,China;Key Laboratory of Geophysical Geodesy,Ministry of Natural Resources,Wuhan 430079,China;Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,China)

机构地区：[1]武汉大学测绘学院,武汉430079 [2]广州市城市规划勘测设计研究院,广州510060 [3]地球空间环境与大地测量教育部重点实验室,武汉430079 [4]自然资源部地球物理大地测量重点实验室,武汉430079 [5]昆明理工大学国土资源工程学院,昆明650093

出　　处：《地球物理学报》2025年第4期1271-1286,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42130101,42074007);云南省基础研究计划项目(202401CF070097);广东省城市感知与监测预警企业重点实验室基金项目(2020B121202019)资助。

摘　　要：北京时间2021年5月22日,青海省玛多县发生M_(S)7.4地震,这是继2008年汶川M_(S) 8.0地震后中国大陆发生的最强震,对玛多地震开展研究有助于更好地揭示强震孕育及余震传播机制.本文采用双差定位算法对主震发生后3个月内的余震数据进行重定位,并采用CAP方法反演了主震及22个余震的震源机制解.以上结果表明,孕震断层总体呈NWW向展布,沿走向自西向东先后呈现为高倾角的“南倾-北倾-南倾”,并且断层在东段出现分叉.主震和大部分余震的震源机制为走滑型,根据震源的应力轴参数,可以确定孕震断层主要受到SWW-NEE向近水平挤压应力控制,符合巴颜喀拉块体的构造环境.随后,本文以重定位后的地震序列为模板,基于匹配定位算法对主震发生10天内的地震波数据进行扫描,最终检测到了2.8倍于中国地震台网中心记录的余震数量,最小完备震级由M1.5下降至M1.0,余震衰减系数p值为0.9~1.1,与典型余震序列一致,并且震后b值随时间呈现上升趋势,反映区域应力逐渐释放的过程.此外,余震的时空迁移呈现出“多峰状”的激活模式,表现为由各凹凸体边缘向周边扩展.最后,本文进一步对余震序列中的重复地震进行了筛选,结合滑动分布与重复余震的发生位置,推测余滑是玛多地震早期余震传播的主要驱动力.On May 22,2021 Beijing time,an M_(S)7.4 earthquake struck Madoi County in Qinghai Province,the strongest earthquake in Chinese mainland since the 2008 M_(S)8.0 Wenchuan earthquake.Investigating the Madoi earthquake provides valuable insights into the preparation of strong earthquakes and the propagation mechanisms of aftershocks.In this study,we relocated aftershocks occurring within three months of the mainshock using the double-difference relocation algorithm and applied the CAP method to invert focal mechanism solutions for the mainshock and 22 aftershocks.Our findings indicate that the seismogenic faults predominantly trend NWW,with a high dip variation of“south-north-south”from west to east and fault bifurcation in the eastern section.The focal mechanisms reveal a predominant strike-slip faulting regime.Stress axis analysis suggests the faults are primarily controlled by near-horizontal compressive stress in a SWW-NEE direction,consistent with the tectonic environment of the Bayan Har block.Using the relocated earthquake sequence as templates,we scanned seismic wave data within 10 days post-mainshock with the Match and Locate method,detecting 2.8 times more aftershocks than reported by the China Earthquake Networks Center and lowering the minimum complete magnitude from M1.5 to M1.0.The calculated aftershock attenuation coefficient p-value of 0.9~1.1 aligns with typical aftershock sequences.As aftershocks decayed,the b-value exhibited an upward trend,reflecting the gradual release of regional stress.Spatial-temporal analysis of aftershocks showed a“multi-peak”activation pattern,with extensions from asperity edges to the periphery.Further analysis of repeated earthquakes within the aftershock sequence,combined with slip distribution and repeated aftershock locations,suggests that residual slip was the primary driver for the propagation of early aftershocks in the Madoi earthquake sequence.

关 键 词：玛多地震 双差定位 CAP 匹配定位算法 余震迁移 

分 类 号：P315[天文地球—地震学]