内蒙狼山—色尔腾山山前活动断裂古地震事件识别及同震垂直位移

Paleo-Earthquake Event and Co-Seismic Vertical Deformation Recognition along the Langshan-Sertenshan Pediment Fault, Inner Mongolia

一、前言狼山—色尔腾山山前活动断裂位于鄂尔多斯高原北部河套盆地西北缘,它与大青山山前活动断裂、乌拉山山前活动断裂共同组成河套断陷北缘断裂系(图1)。狼山—色尔腾山山前活动断裂由北东向狼山山前断裂及近东西向色尔腾山山前断裂组成,分别长约160km和150km,组成河套断陷内临河凹陷的西北部边界。据石油物探资料,临河凹陷内第四系厚2400m,表明临河凹陷第四纪时期的沉积速率达到1mm/a。

Active fault mapping of 1:50 000 had been conducted along the north segment of the Langshan pediment fault and the west segment of the Sertenshan pediment fault in Inner Mongolia in 1994~1995;that have totally about 150km in length.Along the line,we have had 60 Holocene fault scarp parameters;more than 10 Holocene layer dating data;8 trenchings in which 12 dating data obtained.In present paper we discuss the recognition of paleo-earthquake events and the vertical co-seismic deformation along the Langshan-Sertenshan pediment fault on the bases of above-mentioned data.Our synthetic analyses demonstrate that the average interval of paleo-earthquakes occurred in the Langshan pediment fault in mid-late Holocene was 1000a;while for the Sertenshan pediment fault,its late Holocene activity was not obvious,but it had an average interval of 1700a in the early-to-mid Holocene.As to the synthetic analyses of surface fault scarp and trenches,we have obtained the average vertical co-seismic displacement reached 1~2.5m.The average vertical displacement amplitude for each of the paleo-events reached 1.4~4m,in most cases,were 2~4m.