伽师6.4级地震前后震源区视密度变化及其构造意义  

THE APPARENT DENSITY VARIATION OF THE FOCAL AREA BEFORE AND AFTER JIASHI M_(S)6.4 EARTHQUAKE AND ITS TECTONIC SIGNIFICANCE

作　　者：刘代芹 陈石[5,6] 王晓强[2,3,4] 张贝 李杰 吴传勇[7] 卢红艳 LIU Dai-qin;CHEN Shi;WANG Xiao-qiang;ZHANG Bei;LI Jie;WU Chuan-yong;LU Hong-yan(School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station,Urumqi 830011,China;Urumqi Institute of Central Asia Earthquake,China Earthquake Administration,Urumqi 830011,China;Earthquake Agency of Xinjiang Uygur Autonomous Region,Urumqi 830011,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Beijing Baijiatuan Earth Science National Observation and Research Station,Beijing 100095,China;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Science and Engineering,Sun Yat-sen University,Guangzhou 510275,China)

机构地区：[1]中国科学技术大学地球和空间科学学院,合肥230026 [2]新疆帕米尔陆内俯冲国家野外科学观测研究站,乌鲁木齐830011 [3]中国地震局乌鲁木齐中亚地震研究所,乌鲁木齐830011 [4]新疆维吾尔自治区地震局,乌鲁木齐830011 [5]中国地震局地球物理研究所,北京100081 [6]北京白家疃地球科学国家野外观测科学研究站,北京100095 [7]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广州510275

出　　处：《地震地质》2021年第2期311-328,共18页Seismology and Geology

基　　金：新疆维吾尔自治区重点研发专项(2020B03006-2);新疆天山青年计划基金(2017Q010,2017Q064);国家自然科学基金(41774090,41874015);中国科学院战略性先导科技专项(XDB18020201);国家自然科学基金地震联合基金(U1939205);上海合作组织科技伙伴计划(2017E01030);新疆地震局科技创新团队计划(XJDZCXTD2020-1)共同资助。

摘　　要：2020年1月19日新疆维吾尔自治区伽师县发生6.4级逆冲型地震,发震构造为柯坪断裂,震中位于重力监测网内部。文中首先介绍塔里木盆地西缘的重力观测网络系统的基本情况;其次结合“以场求源、场源结合”的思想,利用地震前后2013—2020年塔里木盆地西缘地区的重力重复测量数据,基于贝叶斯重力平差方法得到的点值序列和时变重力信号的场源反演方法,给出等效源反演方法的基本原理和研究区的场源监测能力,并针对实际重复重力观测数据进行测试,反演得到重力时空场源变化特征,获得了研究区地壳内部区域性重力场源动态变化及该区的地震前后多期场源视密度的结构特征;最后,结合2020年伽师6.4级地震发震构造区的重力场变化过程进行了分析和讨论。研究认为:塔里木盆地西缘的重力测网对于伽师M_(S)6.4地震震中周边的场源参数具有较好的分辨能力,地震前区域重力测网在2017年开始出现显著的区域性重力场变化,场源视密度呈现出与柯坪构造系一致的NEE条带特征;在地震前后,场源的视密度出现由正转负的变化过程,震后这种视密度变化与构造走向一致的特征更加明显,且扩展至整个柯坪断裂系范围,说明这些由重力监测获得的场源变化信号与此次地震事件及构造控制的场源环境变化密切相关。文中的研究方法和成果可为时变重力场源特征研究和地震重力前兆信号的分析与解释提供有重要价值的震例参考;同时,对于认识孕震区和断裂带周边的地壳构造运动模式具有重要指示意义。On Jan.19,2020,a magnitude 6.4 thrust earthquake occurred in Jiashi County,Xinjiang Uygur Autonomous Region,and the seismogenic structure is the Keping Fault.The epicenter of the earthquake is located inside the gravity monitoring network,which covers more than 90 gravity monitoring points from Aksu and Kuche to Kashgar and Wucha in the west,Taxkorgan in the south and Hetian area in the southeast.In this paper,the high-precision gravity measurement data in the western margin of the Tarim Basin from 2013 to 2020 before and after the earthquake are used and three absolute gravity measurement points at Kuche,Taxkorgan and Wushi are taken to provide space-time gravity reference constraint.Then,the test board method is used to carry out the field source resolution test,and combined with the theoretical gravity anomaly value of actual measurement points obtained by the gravity forward modeling method,the field source model parameters are obtained by the inversion method.Then,in light of“seeking the source by field and combining the field and source”,using the surface repeated gravity observation data,the point value sequence obtained based on the Bayesian gravity adjustment method,and the field source inversion method for the time-varying gravity signal,the paper evaluates the basic principle of equivalent source inversion method and the field source monitoring capability of the research area.The actual repeated gravity observation data are tested and inversed to obtain spatial and temporal variation characteristics of gravity field sources,as well as the dynamic variation of regional gravity field sources and the structure characteristics of apparent density of multi-period field sources before and after the earthquake in the study area in the last 10 years.Finally,the variation process of gravity field in the seismogenic tectonic area of the 2020 Jiashi magnitude 6.4 earthquake is analyzed and discussed in combination.The study concluded that the gravity survey network on the western margin of the Tarim Basin has

关 键 词：时变重力场 伽师地震 场源反演 贝叶斯平差 视密度变化 

分 类 号：P315.727[天文地球—地震学]