2022年1月8日青海门源M_(S)6.9地震孕震环境和冷龙岭断裂分段延展特征  

The seismogenic model of the Menyuan M_(S)6.9 earthquake on January 8,2022,Qinghai Province and segmented extensional characteristics of the Lenglongling fault

作　　者：赵凌强 孙翔宇[1] 詹艳[1] 杨海波[1] 王庆良[2] 郝明[2] 刘雪华 ZHAO LingQiang;SUN XiangYu;ZHAN Yan;YANG HaiBo;WANG QingLiang;HAO Ming;LIU XueHua(Lhasa National Geophysical Observation and Research Station,State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;The Second Monitoring and Application Center,China Earthquake Administration,Xi′an 710043,China)

机构地区：[1]西藏拉萨地球物理国家野外科学观测研究站,地震动力学国家重点实验室,中国地震局地质研究所,北京100029 [2]中国地震局第二监测中心,西安710043

出　　处：《地球物理学报》2022年第4期1536-1546,共11页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2017YFC1500103);国家自然科学基金面上项目(41474057);地震动力学国家重点实验室自由课题(LED2021A01,LED2019B06)共同资助.

摘　　要：2022年1月8日1时45分,青海省海北州门源县(北纬37.77°,东经101.26°)发生6.9级地震,发震断裂为祁连—西海原断裂冷龙岭段(以下简称冷龙岭断裂),这是冷龙岭断裂继2016年1月21日M_(S)6.4地震之后发生的又一次破坏性中强地震.本文在三条跨过冷龙岭断裂不同区段的大地电磁剖面数据三维反演出的电性结构约束下,解译出该断裂不同区段的深部延展特征,并进一步探讨2022年门源M_(S)6.9地震动力学模式和孕震构造模型.冷龙岭断裂整体上表现为延伸至下地壳的大型高低阻电性边界带的特征,符合以往大地电磁探测结果约束的大型走滑断裂带的电性结构特点.2016年门源M_(S)6.4地震和2022年门源M_(S)6.9地震均发生在冷龙岭附近的高低阻体边界带并靠近高阻一侧.冷龙岭断裂西段构造较为复杂,主断裂为近直立的电性边界带,北侧的肃南—祁连断裂和民乐—大马营断裂是其伴生断裂并分担了逆冲分量,断裂中东段表现为单一向南倾向的电性边界带.冷龙岭断裂自西向东运动性质存在着以走滑为主向逆冲兼具走滑转变的趋势,这与2022年M_(S)6.9地震和2016年M_(S)6.4地震两次地震显示出不同发震机制相符合.结合研究区GPS和精密水准场资料分析,冷龙岭断裂是青藏高原北东向挤压扩展应力转化为南东向迁移和逃逸的核心区域,这种应力方向转变导致冷龙岭断裂发生强烈左旋走滑作用是发生2022年1月8日青海门源M_(S)6.9地震的动力学来源.随着青藏高原北东向推挤作用的持续进行以及冷龙岭断裂在南北两侧表现为重要物性差异带的特点,判断该断裂未来依旧是强震孕育风险区.At GMT+81∶45 on January 8,2022,an earthquake with a magnitude of 6.9 occurred in Menyuan Town,Haibei Prefecture,Qinghai Province(N37.77°,E101.26°).The seismogenic fault is the Lenglongling section(also named after Lenglongling fault)of the Qilian-West Haiyuan fault system.This is another destructive moderately strong earthquake that occurred on the Lenglongling fault after the M_(S)6.4 earthquake on January 21,2016.In this paper,we constrained three-dimensional inverse electrical structures across the different segments of the Lenglongling fault using three magnetotelluric(MT)profiles,interpreted the deep extensional characteristics of the fault,and further discussed the dynamic model of the 2022 M_(S)6.9 earthquake.The Lenglongling fault is generally characterized by large-scale high-low resistivity boundary zone that extends downward to the lower crust,which is consistent with the previous cognition of electrical structure for large-scale strike-slip fault.The 2016 M_(S)6.4 and 2022 M_(S)6.9 earthquakes both occurred in the boundary zone of high and low resistivity near the Lenglongling fault and close to the side of high resistivity.The structure of the west section of the Lenglongling fault is relatively complex.The main fault is shown by a nearly vertical electrical boundary zone.The Sunan-Qilian fault and Minle-Damaying fault in the north are associated faults of Lenglongling fault and share the thrust component.The middle and east segments of the fault are characterized by the south-dipping electrical boundary zones.The kinematics of Lenglongling fault has a trend of transformation from strike-slip to the west towards strike-slip with thrusting component to the east,which is compatible with the varied seismogenic mechanisms for the 2016 M_(S)6.4 earthquake and 2022 M_(S)6.9 earthquake in different sections.Combined with the data analysis of GPS and precise leveling field in the study area,we suggest that the Lenglongling fault is the core area where the NE-trending compressional stress field induced by

关 键 词：门源M_(S)6.9地震 大地电磁三维反演 冷龙岭断裂 孕震模式 古浪推覆体 

分 类 号：P315[天文地球—地震学] P319[天文地球—固体地球物理学]