墨脱断裂带波东-西让段电性结构及其地震意义  

Electrical structure and seismic implication of Motuo fault zone in Bodong-Xirang area

作　　者：王刚[1,2] 方慧 WANG Gang;FANG Hui(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Science,Langfang 065000,China;National Research Center of Geo-exploration Technology,Langfang 065000,China)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,廊坊065000 [2]国家现代地质勘查工程技术研究中心,廊坊065000

出　　处：《地球物理学进展》2023年第6期2430-2439,共10页Progress in Geophysics

基　　金：中国地质调查局地质调查项目(DD20230233,DD20230324,DD20221638,JKYZD202329);国家自然科学基金项目(41804075)联合资助。

摘　　要：为了研究喜马拉雅东构造结墨脱断裂带的构造格架和稳定性,首次在墨脱断裂带开展大地电磁测深观测,通过张量采集方式充分发挥实测数据的约束作用以提高结果的可靠性.位于波东、地东和西让村的三条大地电磁测深(MT)剖面结果揭示了巴登则断裂、月尔东断裂的展布形态,并且发现了F1~F8等一系列可能存在的隐伏断裂,剖面电性结构从北西到南东可分为高阻的构造混杂岩体、念青唐古拉群和拉萨地体.三条大地电磁测深剖面的电性结构模型表明巴登则和月尔东等断裂均倾向南东,向下延伸深度大于2 km;剖面南侧的F6断裂近于直立,F7断裂倾向北西且倾角较大;整体上看,向剖面中部断裂逐渐变陡,呈现为向深部汇聚的负花状构造.这可能是墨脱断裂带在波东-西让段未受区域地震明显影响以及大地震发生频次较低的主要原因.根据F6断裂与月尔东断裂的组合关系,整体看来F6断裂更有可能是墨脱断裂带的主控断裂.In order to study the tectonic framework and stability of the Motuo fault zone in the eastern Himalayan syntaxis,a Magnetotelluric Sounding(MT)observation was carried out for the first time in Bodong-Xirang area.During the collection of magnetotelluric data,full tensor components were recorded to improve the reliability of results.The electrical structure of the three magnetotelluric sounding profiles located in Bodong,Didong and Xirang villages revealed the subsurface geometry of the Badongze and Yuedong faults,and discovered a series of buried faults such as F1~F8.From northwest to southeast,the electrical structure can be divided into the resistive tectonic melange,Nianqing Tanggula group,and Lhasa terrane.The electrical structure of the three magnetotelluric sounding profiles indicate that the Badongze and Yuedong faults both extend downwards to the southeast for a depth greater than 2 km.The F6 fault on the southern side of the profiles is nearly vertical,while the F7 fault leans northwestward.In general,the faults gradually steepen towards the middle of the profiles,presenting a negative-flower structure.This may be the reason why the activity risk of the Motuo fault zone in the Bodong-Xirang section has not been increased by the regional earthquakes and the frequency of major earthquakes is relatively low.According to the relationship between the F6 and the Yuedong faults,the F6 is more likely to be the main controlling fault of the Motuo fault zone.

关 键 词：墨脱断裂带 构造格架 大地电磁测深 电性结构 地震 

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