大地电磁数据揭示的1303年洪洞8级地震区精细结构  

THE SEISMOGENIC STRUCTURE OF THE 1303 HONGTONG M8 EARTHQUAKE INFERRED FROM MAGNETOTELLURIC IMAGING

作　　者：赵凌强 詹艳[1,2] 王庆良[3] 孙翔宇[1,2] 韩静 操聪 张松[3] 蔡妍[4] ZHAO Ling-qiang;ZHAN Yan;WANG Qing-liang;SUN Xiang-yu;HAN Jing;CAO Cong;ZHANG Song;CAI Yan(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;National Continental Rift Valley Dynamics Observatory of Taiyuan,Institute of Geology,China Earthquake Administration,Beijing 100029,China;The Second Monitoring and Application Center,China Earthquake Administration,Xi′an 710043,China;Institute of Geophysics,China Earthquake Administration,Beijing 100083,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,北京100029 [2]中国地震局地质研究所,山西太原大陆裂谷动力学国家野外科学研究站,北京100029 [3]中国地震局第二监测中心,西安710054 [4]中国地震局地球物理研究所,北京100083

出　　处：《地震地质》2022年第3期686-700,共15页Seismology and Geology

基　　金：山西太原大陆裂谷动力学国家野外科学观测研究站项目(NORSTY20-07);国家重点研发计划项目(2017YFC1500103,2017YFC1500102);国家自然科学基金(41474057,41590860,61627824);地震动力学国家重点实验室开放基金(LED2019B06)共同资助。

摘　　要：文中利用相位张量分解技术、三维NLCG反演方法对一条跨过1303年洪洞8级地震区、长160km的大地电磁剖面的数据进行了分解和反演计算,再结合研究区及其附近的形变场、最新地震地质和地球物理调查结果以及2008年1月—2012年12月的小地震精定位结果等资料进行综合分析。研究表明,霍山山前断裂是研究区内明显的大型电性边界带,在中深部表现为低阻特征,贯穿了整个地壳尺度,该断裂为NNE走向的右旋正断裂,可能是划分鄂尔多斯地块和华北地块的基底断裂。以霍山山前断裂为界,西侧鄂尔多斯地块表现为层状的稳定构造环境,而东侧华北地块的中下地壳岩石圈破坏严重且存在减薄的趋势。大地电磁探测结果支持1303年洪洞8级地震的发震断裂为霍山山前断裂的观点,地震可能发生在霍山山前断裂下方的低阻体中,震源深度可能介于10~20km之间。1303年洪洞8级地震的孕震环境可能受多重因素控制,研究区东侧中下地壳可能存在的软流圈物质不断上涌引起了华北地块的区域拉张作用,进而导致霍山山前断裂发生倾向滑动可能是地震的主控因素。In the early Autumn of 1303AD,a large earthquake with a tremendous impact occurred in the northeast of Hongtong County,Shanxi Province,and this earthquake was the first major earthquake of M 8 identified by seismogeologists through the study of historical records.The magnitude of the earthquake was large,and the isoseismal line was distributed in the NNE direction.The meizoseismal area was mainly located in the densely populated Fenwei fault-depression zone,so it caused great economic and property losses and casualties at that time,and left a lot of historical data.Most scholars have identified the seismic rupture of this earthquake as the Huoshan piedmont fault,but the current research methods are focused on geological methods such as seismogeological surveys and trenching.At present,in addition to seismogeological investigation and research,there is an urgent need for detailed geophysical exploration of the fine structure and seismogenic environment of the 1303 Hongtong earthquake area and the deep structure of the Huoshan piedmont fault.The phase tensor decomposition techniques and NLCG three-dimensional inversion were used to process the data of a MT profile,which is 160km in length and across the 1303 M 8 Hongtong earthquake area,combined with the present-day crustal vertical motion data(including GPS and leveling data)and the latest geological and geophysical survey results in and around the study area.The results show that the Huoshan piedmont fault is an obvious large electrical boundary zone in the study area.In the middle and deep part,it is a low resistivity belt,which runs through the whole scale of the crust.The fault is a NNE-trending dextral normal fault,which may be the basement fault dividing Ordos block and North China block,extending from the surface to 40km underground.The Lishi Fault also shows as an obvious electrical boundary zone,which may be a large-scale fault system in the study area.With the Huoshan piedmont fault as the boundary,the Ordos block and North China block on the east and we

关 键 词：大地电磁 1303年洪洞8级地震 临汾盆地 霍山山前断裂 

分 类 号：P315.721[天文地球—地震学]