InSAR数据约束的2021年西藏比如M_(W)5.8地震同震滑动分布及库仑应力变化  

COSEISMIC SLIP DISTRIBUTION OF THE 2021 M_(W)5.8 BIRU(TIBET,CHINA)EARTHQUAKE AND THE COULOMB STRESS VARIATION

作　　者：于书媛[1,2] 张国宏 张迎峰[3] 丁娟[1,2] 张建龙[4] 范晓冉 王绍俊 YU Shu-yuan;ZHANG Guo-hong;ZHANG Ying-feng;DING Juan;ZHANG Jian-long;FAN Xiao-ran;WANG Shao-jun(Anhui Earthquake Agency,Hefei 230031,China;Anhui Mengcheng National Geophysical Observatory,Mengcheng 233527,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Earthquake Agency of Tibet Autonomous Region,Lhasa 850000,China;Geophysics Department,School of Earth Sciences,Yunnan University,Kunming 650500,China)

机构地区：[1]安徽省地震局,合肥230031 [2]安徽蒙城地球物理国家野外科学观测研究站,蒙城233527 [3]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [4]西藏自治区地震局,拉萨850002 [5]云南大学地球科学学院,地球物理系,昆明650500

出　　处：《地震地质》2022年第5期1190-1202,共13页Seismology and Geology

基　　金：国家自然科学基金(41802224);中国地震局地震科技星火计划项目(XH23019YC);安徽蒙城地球物理国家野外科学观测研究站联合开放基金(MENGO-202114)共同资助。

摘　　要：文中运用D-InSAR技术获取的2021年3月19日西藏比如县M_(S)6.1地震的同震形变场显示:升、降轨LOS向同震位移场的长轴为NE向,其中最大抬升量和沉降量分别约为5cm和6cm;在此基础上,基于Okada模型反演断层面的精细滑动分布特征。反演结果表明近场残差得到有效控制,其中发震断层参数为:走向228°,为SE倾向断层,宏观震中位于(31.94°N,92.87°E),矩震级为M_(W)5.8,平均滑动角为-56.42°,最大滑动量达0.2m,倾角为55°。最后,运用Column33软件计算以反演断层为接收断层的不同深度的同震库仑应力变化,结果显示比如地震震中附近产生了明显的应力降,深部断层滑动量很小。后续地震事件通常发生在5~15km深度,这与相应深度的应力增加区域一致;以班公湖-怒江断裂和聂荣北断裂为接收断层的应力变化显示,比如地震在2条断裂的部分区域产生了应力加载,库仑破裂应力值ΔCFS>0.01MPa,需要引起关注。结合地表形变观测资料和前人的研究成果初步认为,比如M_(W)5.8地震的发震断层为NE向隐伏次级断裂,位于班公湖-怒江断裂带西段北侧,断裂活动方式以正断为主,兼具少量走滑分量,发震断层与主断层的关系需要通过野外地质调查资料综合确定。On March 19,2021,an earthquake of M_(W)5.8 occurred in Ruju County,Tibet.The epicenter of the earthquake is located to the west of Xiaqu town in the Qiangtang Basin in the north of the Qinghai Tibet Plateau.The regional structure around the earthquake is complex and there are many faults developed there.To the south of the epicenter is Peak Shaqiongya and to its west is Peak Ceduo,both are high-altitude peaks.Since 1970(up to July 22,2021),27 earthquakes with M_(W)≥5 have occurred within 200km of the area,most of which are of normal faulting,indicating that tensile stress plays a dominant role in the area.The largest earthquake is the Naqu earthquake with M_(W)5.9 that occurred near the Bengco Fault in 1972.Therefore,this earthquake is a rare medium strong earthquake in this area.Studying the seismogenic structure of this earthquake has reference significance for understanding the geological structure,fault movement characteristics and seismic rupture attributes of normal faulting earthquakes in this area.In this paper,the coseismic deformation field of this earthquake is obtained by using D-InSAR technology.It shows that the maximum uplift and subsidence are 5cm and 6cm respectively,the long axis direction is NE,and the LOS deformation signs of ascending and descending orbit are the same.It is preliminarily determined that the seismogenic fault is a normal fault,striking NE.On this basis,based on the SDM software and Okada method,the initial seismogenic fault is constructed with a length of 27.56km(92.78°~93.00°E),a width of 20km(set in the SDM program),a dip angle of 50°~63°,and a rake angle of-150°~0°;the smoothing factor is set to 0.08,and the maximum number of iterations is 10000.Secondly,the fault dip angle of the selected range is tested with a step of 1°,and the optimal fault dip angle is determined to be 55°.On this basis,a single fault model is used to divide the fault plane into 1km×1km fine slip distribution model of 1km sub fault structure.Finally,the distribution characteristics of coseis

关 键 词：比如地震 INSAR 同震形变场 断层滑动 静态库仑应力 

分 类 号：P315.2[天文地球—地震学]