鄂尔多斯北缘断裂托克托段晚第四纪活动特征  

Late Quaternary Activity Characteristics of Tuoketuo Section of the Ordos Northern Fault

作　　者：刘华国 贾启超 龚飞 Liu Huaguo;Jia Qichao and Gong Fei(China Earthquake Disaster Prevention Center,Beijing 100029,China)

机构地区：[1]中国地震灾害防御中心,北京100029

出　　处：《震灾防御技术》2022年第2期242-251,共10页Technology for Earthquake Disaster Prevention

基　　金：中国地震局城市活断裂探测与地震危险性评价项目(14406033401);鄂尔多斯北缘断裂精细结构及地震危险性评价(1840616030203)。

摘　　要：鄂尔多斯北缘断裂作为河套断陷带和鄂尔多斯地块的边界断裂,研究其晚第四纪活动特征,对于科学评价黄河流域内蒙古河套段的地震危险性具有重要意义。本文利用野外地质调查、微地貌测量、浅层人工地震勘探及钻孔联合剖面探测相结合的方法,综合地层年代样品测试结果,确定了该断裂托克托段的准确位置和最新活动特征。研究结果表明,鄂尔多斯北缘断裂托克托段沿线构造地貌不发育,推测断裂的最新活动可能尚未达到地表,地表的地貌陡坎应为河流侵蚀成因。断裂在深、浅地震反射剖面上表现为“Y”字形的张性断裂系,主断裂倾向北,分支断裂倾向南,整体上陡下缓,具有多个地堑式分布的特点。跨断裂钻孔联合剖面上显示,单个分支断裂的同震垂直位移量为2~2.5 m,最新活动时代为43.5~70 ka。鄂尔多斯北缘断裂是一条晚更新世活动的深大断裂,具有一定的地震危险性。As a large-scale boundary fault between Hetao fault zone and Ordos uplift,the Ordos northern fault is of great significance to scientifically evaluate the seismic risk of the Yellow River Basin nearby Hetao area by studying its late Quaternary activity characteristics.In this paper,the accurate location and the active characteristics of the fault are comprehensively analyzed and restricted by using the methods of field geological survey,micro geomorphic survey,geophysical exploration and borehole combined profile detection,combined with the test results of stratigraphic age.The results show that the tectonic landform along the fault in the northern edge of Ordos is not significant.It is speculated that the latest activity of the fault may not reach the surface,and the geomorphic scarps on the surface may caused by river erosion.The deep and shallow seismic reflection sections show a Y-shaped tensional fault system,and the main fault dip is North,the branch fault dip south,and the global feature is up steep and down slow,with the characteristics of multiple graben distribution.According to the borehole joint profile detection carried out according to the geophysical test results,the coseismic vertical displacement of a single branch fault is about 2~2.5 m,and the latest activity age is 43.5~70 ka.In a word,it is a deep and large boundary fault active in the late Pleistocene,which has a certain seismic risk.

关 键 词：浅层人工地震 钻孔联合剖面 鄂尔多斯北缘断裂 晚更新世活动 

分 类 号：P542[天文地球—构造地质学]