嫩江断裂带北段的第四纪活动特征初步研究

摘要

The Nenjiang fault zone (NJFZ) is the western boundary fault of the Songliao basin, and the Quaternary tectonic deformation of which remains to be understood well because of unfavorable working conditions such as intensive Quaternary coverage. This paper focuses on the Quaternary tectonic activities of the northern section of the NJFZ based on the integrated results of field geological investigation, MT data inversion and P-wave velocity structure. Abundant tectonic evidences are observed along the northern section of the NJFZ such as geomorphic scarps, bedrock landslide, crumple deformation of strata, vertical scratch, and bedrock collapse and linear sag ponds.The trench reveals that at least one normal paleo-event occurred between (80.9±4.6) ka BP and (62.9±2.3) ka BP, which caused 1.5 m vertical displacement with an estimated magnitude MS 7.1-7.3, which means that the NFFZ was activated during the late Pleistocene. The results not only help us to understand the Quaternary tectonic deformation process of the NJFZ and the Songliao basin, but also provide references for the assessment of the earthquake potential along the NJFZ and its neighbor areas.%嫩江断裂带是松辽盆地的西边界断裂,但受第四系强覆盖等研究条件的限制,前人对该断裂第四纪构造活动的研究较少.本文针对该断裂带北段开展了野外地质调查,并综合大地电磁测深和纵波速度结构等结果,初步研究了嫩江断裂带北段的第四纪活动特征.调查发现,该断裂北段主要发育地貌陡坎、基岩滑坡、地层揉皱变形、近垂直擦痕、基岩崩塌与线性断塞塘等特征.探槽古地震研究揭示断裂带北段在(80.9±4.6)—(62.9±2.3)ka BP曾发生1次古地震事件,运动方式为正断,垂直位移量约1.5m,震级约为MS 7.1-7.3,断裂在晚更新世曾发生过强烈活动.研究结果有助于认识了解该断裂和松辽盆地的第四纪构造变形过程,并为评价该断裂及邻区的地震活动潜势提供参考.