2020年M_(W)6.0柯坪塔格地震的变形特征及其对周边地震危险性的启示  

THE DEFORMATION OF 2020 M_(W)6.0 KALPINTAGE EARTHQUAKE AND ITS IMPLICATION FOR THE REGIONAL RISK ESTIMATES

作　　者：张迎峰[1] 单新建[1] 张国宏[1] 李成龙 温少妍[2] 解全才[3] ZHANG Ying-feng;SHAN Xin-jian;ZHANG Guo-hong;LI Cheng-long;WEN Shao-yan;XIE Quan-cai(State Key Laboratory of Earthquake Dynamics,Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Earthquake Agency of Xinjiang Uygur Autonomous Region,Urumqi 830011,China;Key Laboratory of Earthquake Engineering and Engineering Vibration,Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,新疆帕米尔陆内俯冲国家野外科学观测研究站,北京100029 [2]新疆维吾尔自治区地震局,乌鲁木齐830011 [3]中国地震局工程力学研究所,地震工程与工程振动重点实验室,哈尔滨150080

出　　处：《地震地质》2021年第2期377-393,共17页Seismology and Geology

基　　金：国家重点研发计划项目(2019YFC1509205);中国地震局地质研究所基本科研任务专项(IGCEA2001);国家自然科学基金(41631073)共同资助。

摘　　要：塔里木盆地基底与天山造山带之间的持续挤压会聚,不仅造就了天山不断隆升的山体,也导致了遍布整个造山带的破坏性地震,而位于其山体两侧盆山交接区域的破坏性地震更是严重威胁着沿线居民和基础设施的安全。文中以2020年M_(W)6.0柯坪塔格地震为切入点,获取了该地震的InSAR同震形变场,并基于强震台加速度记录经双重积分得到了位移矢量,以此为约束反演了本次地震发震断层的运动学参数;此外,综合该区域历史地震和构造特征的最新研究成果,讨论了本次地震与历史地震之间的关系,进而评估了柯坪塔格褶皱带周边的地震危险性。研究表明,2020年柯坪塔格M_(W)6.0地震的破裂范围受限于褶皱构造,其产生的地表形变促进了柯坪塔格前缘褶皱的抬升,由此推测该地震导致了褶皱带下伏沉积层底部滑脱面的位错,是褶皱带内SN向挤压应力集中释放的表现。包括本次地震在内的区域历史地震(1902年M_(W)7.7伽师地震、1996年M_(W)6.3伽师地震和1997—2003年伽师地震群)均可以解释为塔里木盆地基底向西南天山下插过程中地壳对不同部位应力积累特征的响应。经简单计算所得的结果表明,在不考虑障碍体的情况下,柯坪塔格周边可发生M_(W)7.0以上地震。The continuous collision between Tian Shan and Tarim Basin causes not only the uplift of mountains,but also the earthquakes across the entire Tian Shan,particularly in the transient zone from mountains to the adjacent basins,where the critical infrastructures and residents are seriously under threat from these earthquake hazards.On 19 th January,2020,an earthquake occurred in the Kalpintage fold thrust belt in the southwest Tian Shan foreland.We call this event the 2020 M_(W)6.0 Kalpintage earthquake,which is the first moderate earthquake captured by modern geodetic measurement techniques.This event therefore provides a rare opportunity to look into the local tectonics and seismic risk in southwest Tian Shan.In this study,we obtained the coseismic deformation of 2020 M_(W)6.0 Kalpintage earthquake from Sentinel-1A SAR and strong motion data,and then inverted its kinematic slip model.We derived the InSAR interferograms from both ascending and descending tracks.Both of them present similar deformation patterns,two deformation peaks over the Kalpintage anticline.That means:(1)The surface deformation is dominated by vertical displacement,and (2)the coseismic rupture plane is highly suspected to be the shallowly dipping decollement at the base of the sediment cover.We got the 3-D displacements of 6 strong motion stations by double integrating the strong motion acceleration signals.The result shows tiny displacement on the strong motion stations,except for the Xikeer station,which locates at the front of the Kalpintage anticline,where the InSAR interferograms are seriously incoherent.Two slip models can equally fit to the ascending and descending InSAR interferograms:One is a strike slip model with strike of N-S,the other is a thrust model with strike of E-W.This ambiguity in the slip models for the M_(W)6.0 Kalpintage earthquake is caused by (1)the extremely small dip angles of the causative fault,(2)the inherent shortcomings of the InSAR measurements i.e.the 1-D measurements along the line of sight,the polar orbiting

关 键 词：2020年柯坪塔格地震 INSAR 强震动 地震危险性 

分 类 号：P315.2[天文地球—地震学]