依兰—伊通断裂带舒兰段深部电性结构研究

Study on Deep Electrical Structure Characteristics of the Shulan Section of the Yilan-Yitong Fault Zone

依兰-伊通断裂带是划分我国中蒙和中朝2个活动地块的重要边界断裂,也是东北地区规模最大的断裂系统,以往研究认为该断裂活动较弱,但该断裂舒兰段在全新世有过强烈活动。针对这一问题,2021年在穿过依兰-伊通断裂带舒兰段位置布设了一条大地电磁剖面,对所获取的14个宽频测点数据进行了精细化处理和二维反演,获得了断裂带及其两侧地块的深部电性结构特征。结果表明:依兰-伊通断裂带舒兰段及其邻近地区电性结构表现为东西横向分块的特点,其中主断裂呈现延伸至中下地壳的中低阻条带,强度较弱,其东西两侧为高阻,强度较强。结合中国大陆其他活动断裂区的大地电磁探测结果,推测依兰-伊通断裂带舒兰段的电性结构分布特点有利于断层活动和形变累积,未来需要注意其地震孕育的风险。

The Yilan-Yitong fault zone is an important boundary of the China-Mongolia active block and the China-Korea active block,and it is the largest fault system in Northeast China.The latest research results show that the Shulan segment of the Yilan-Yitong fault zone was intensively active in the Holocene,which challenges the previous conclusion that the fault activity in the Holocene was weak.In this paper,a broadband magnetotelluric profile data obtained at 14 measuring sites across the Shulan section of the Yilan-Yitong fault zone have been refined and inversed in 2D space,and the characteristics of the deep electrical structure along the Shulan section of the Yilan-Yitong fault zone have been obtained.The characteristics of the deep electrical structure of the blocks on both sides of the Shulan section have been obtained too.The results show that the electrical structure of the Shulan section and its adjacent areas is characterized by East-West lateral blocking;the main fault of the Shulan section is embeded in the unstable medium-low-resistivity bands extending to the middle-lower-crust,on east side and west side of the Shulan section there exist the high-resistivity bodies.Referring to the magnetotelluric detection results of other active-fault areas in Chinese Mainland,we speculate that the electrical structure feature of the Shulan section is conductive to stress accumulation and faulting.There exists earthquake risk in this area in the future.