滇东北地区三维电性构造研究  

Three-dimensional electrical conductivity structure in Northeast Yunnan, China

作　　者：梁萱 唐新功[1] 余俊虎 胡文宝[1] LIANG Xuan;TANG XinGong;YU JunHu;HU WenBao(Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education,Yangtze University,Wuhan 430100,China)

机构地区：[1]“油气资源与勘探技术”教育部重点实验室(长江大学),武汉430100

出　　处：《地球物理学报》2023年第7期2860-2874,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41874119,41674107,42174083)资助。

摘　　要：滇东北地区位处不同构造分区的交界地带,发育有多样的断裂构造,其中昭通—鲁甸断裂和小江断裂带的部分区段均具备积累高应力的条件,具有较强的孕震潜力.本文基于覆盖巧家、东川、鲁甸等地区采集的区域大地电磁阵列观测数据,通过大地电磁三维反演,获得了该地区的三维电性结构的水平和垂直切片,完整地揭示了滇东北地区的深部电性结构特征.反演结果表明,昭通—鲁甸断裂在10 km深度以内发育有多个局部高阻区,小江断裂带的巧家—东川段的东侧、东西两支交汇处在上地壳均表现为高阻,这些区域均展示出更强的孕震能力.根据低阻异常的分布,推测昭通—鲁甸断裂和小江断裂下方的低阻构造在中下地壳的多个位置发生连通.本文将研究区的地表热流、岩石圈有效弹性厚度、地震与电性结构结合分析,推测在滇东北深部低阻层可能存在下地壳流,并且下地壳流的塑性流动为鲁甸的地震活动提供了深部动力来源.Northeast Yunnan is located at the junction of different tectonic divisions.A variety of faults have developed in northeastern Yunnan,among which some sections of Zhaotong—Ludian fault and Xiaojiang fault can accumulate high stress and have strong seismogenic potential.Based on the regional magnetotelluric array observation data collected in Qiaojia,Dongchuan,Ludian and other regions,this paper obtained horizontal and vertical slices of three-dimensional electrical structures using three-dimensional magnetotelluric inversion,which completely reveals the deep electrical structure in northeastern Yunnan.The inversion result shows that Zhaotong—Ludian fault has developed several local high resistance bodies within 10 km depth.The southwest side of the Qiaojia—Dongchuan section and the intersection of the east section of Xiaojiang fault all show high resistance in upper crust.These regions all show stronger seismogenic ability.This paper combines surface heat flow,effective elastic thickness of the lithosphere,earthquakes and the electrical structure for analysis.It is speculated that the deep low-resistivity layer in northeastern Yunnan may be the lower crust channel flow whose plastic flow provides the deep power source for earthquakes in Ludian.

关 键 词：大地电磁测深(MT) 三维电性构造 昭通-鲁甸断裂带 小江断裂带 地壳流 地震 

分 类 号：P541[天文地球—构造地质学]