【摘要】 野外调查表明 ,恒山北缘断裂断错了恒山北侧的洪积扇和恒山冲沟沟口的Ⅰ级阶地。地层测年资料表明 ,恒山北缘洪积扇中部、后缘以及恒山冲沟沟口Ⅰ级阶地的表层由距今约 5 2 0 0～ 6 80 0a的地层组成。位于恒山山前开挖的何庄及牛槽峪探槽揭示恒山北缘断裂在全新世早期以来曾发生过 3次古地震事件。这 3次古地震事件分别发生在 2 2 6 0± 190aBP～ 4 370±15 0aBP、接近 5 6 2 8± 15 0aBP和 80 83± 2 5 0aBP～ 84 30± 72 0aBP。 3次古地震事件的间隔为 2 313a及2 6 2 8a ,平均 2 4 71a。古地震事件的同震垂直位移为 1 0～ 3 0m。由于该断裂最新活动的离逝时间已超过全新世时期的古地震间隔 ,今后该断裂具备发生强震的可能 ,需加强观测。更多还原

【Abstract】 The NEE-trending northern piedmont fault of Hengshan Mountain is located at the southern side of the Datong basin, Shanxi Province. It is one of the major three boundary faults controlling Cenozoic sedimentation of the Datong basin. The largest thickness of the Cenozoic sediments along the northern piedmont fault of Hengshan Mountain reached 3800m (Fig.1). The largest thickness of the Cenozoic sediments along the other two main boundary faults that are the Kouquan fault and the piedmont fault of Liulengshan Mountain is 1500～1800m.It is indicated by field investigation that a segment as long as 130km of the northern piedmont fault of Hengshan Mountain has been active in the Holocene, and its geomorphic characteristic dislocated by normal dip-slip activity is very obvious. Bed triangle faces appear along the piedmont, which are magnificent sight. Outcrops of the fault that dislocate back edges of pluvial fans and front edge of the 1st terraces of gully mouths of the Hengshan Mountain can be seen along the fault. The dating data show that the near surface layer of the 1st terrace and the middle and back edges of pluvial fans is of 4000 ～ 7000 a.B.P. (Figs.2 & 3).Two exploratory trenches have been made during our investigation, at the Hezhuang and Niucaoyu along the northern piedmont of Hengshan Mountain. The location of the Hezhuang trench was chosen in front of gully 1st terrace along the piedmont of Hengshan Mountain(Fig. 4). The location of the Niucaoyu trench was chosen in middle of a pluvial fan, 0.7km from the mail fault face of the piedmont fault (Fig.6). The two trenches are of 72km apart. The two trenches open out multiple active evidences of the northern piedmont fault of Hengshan Mountain in Holocene time and the results can be corresponded to each other. It shows from two trenches that there has been 3 times of paleo-seismic events since Early Holocene (Fig.5 & 7). They occurred nearly at 2260±190～4370±150a.B.P., 5628±150a. B.P., and 8083±250～8430±720a.B.P.. The recurrence time of these 3 events would be 2313a and 2628a, and the average interval was 2471a. The co-seismic vertical displacement of the 3 events reached 1.0～3.0m.These new data have impotent significance for earthquake safety assessment of the Datong area.更多还原