山西大同盆地恒山北缘断裂全新世古地震活动
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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。
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.
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.
引文
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程绍平、杨桂枝,1996,大同-阳原盆地南缘断裂带的第四纪分段和构造地貌变异,地震地质,18(4),289～300。
邓起东、王克鲁、汪一鹏等,1973,山西隆起区断陷地震带地震地质条件及地震发展趋势概述,地质科学,(1),37～47。
邓起东、于贵华、叶文华,1992,地震地表破裂参数与震级关系的研究,活动断裂研究2,247～264,北京:地震出版社。
邓起东、徐锡伟,1995,山西断陷盆地带的活动断裂和分段性研究,现代地壳运动研究6,225～242,北京:地震出版社。
邓起东、米仓伸之、徐锡伟等,1994,山西高原六棱山北麓断裂晚第四纪运动学特征初步研究,地震地质,16(4),339～343。
丁国瑜、卢演俦,1983,华北地块新构造基本特点的讨论,华北地震科学,1(2),1～9。
段瑞涛、方仲景,1995,六棱山北麓断裂新活动特征,地震地质,17(3),207～213。
刘光勋、肖振敏,1982,山西地堑系及其地震构造特征,第二届全国地质构造学术会议论文选集(第三卷),66～74,北京:科学出版社。
马 谨,1992,对大同-阳高地震发震构造的讨论,地震地质,14(1),10～11。
聂宗笙,1988,大青山山前断裂带,鄂尔多斯周缘活动断裂系,46～65,北京:地震出版社。
苏宗正、程新源,1992,1989年大同-阳高地震的地质环境与地震构造,山西地震,(1),19～30。
苏宗正、安卫平、刘 巍等,1994,大同断陷盆地及其大震危险性,山西地震,(4),21～32。
闻学泽,1995,活动断裂地震潜势的定量评估,1～150,北京:地震出版社。
徐锡伟,1989,山西地堑系的新构造活动特征及其形成机制,博士论文,1～242,北京:国家地震局地质研究所。
徐锡伟、车用太、杨主恩等,1991,大同-阳高地震群发震构造模式的讨论,中国地震,7(2),77～85。
徐锡伟、米仓伸之、铃木康弘,1996,山西六棱山北麓晚第四纪不规则断裂作用的地貌学研究,地震地质、18(2),168～180。
徐锡伟,1998,山西高原恒山和六棱山两北麓断裂的运动学基本特征及其地震危险性评估,活动断裂研究6,74～87,北京:地震出版社。
杨景春,1996,大同盆地新构造运动与构造地貌特征,山西地堑系新生代沉积与构造特征,219～234,北京:科学出版社。
TokihikoMatruda,1981,ActivefaultsanddamagingearthquakesinJapanMacroseismiczoningandprecautionfaultzones,EarthquakePredictionAnInternationalReview,MauriceEwingSeries4,Am.GeophysUnion.279～289。
程绍平、杨桂枝,1996,大同-阳原盆地南缘断裂带的第四纪分段和构造地貌变异,地震地质,18(4),289～300。
邓起东、王克鲁、汪一鹏等,1973,山西隆起区断陷地震带地震地质条件及地震发展趋势概述,地质科学,(1),37～47。
邓起东、于贵华、叶文华,1992,地震地表破裂参数与震级关系的研究,活动断裂研究2,247～264,北京:地震出版社。
邓起东、徐锡伟,1995,山西断陷盆地带的活动断裂和分段性研究,现代地壳运动研究6,225～242,北京:地震出版社。
邓起东、米仓伸之、徐锡伟等,1994,山西高原六棱山北麓断裂晚第四纪运动学特征初步研究,地震地质,16(4),339～343。
丁国瑜、卢演俦,1983,华北地块新构造基本特点的讨论,华北地震科学,1(2),1～9。
段瑞涛、方仲景,1995,六棱山北麓断裂新活动特征,地震地质,17(3),207～213。
刘光勋、肖振敏,1982,山西地堑系及其地震构造特征,第二届全国地质构造学术会议论文选集(第三卷),66～74,北京:科学出版社。
马 谨,1992,对大同-阳高地震发震构造的讨论,地震地质,14(1),10～11。
聂宗笙,1988,大青山山前断裂带,鄂尔多斯周缘活动断裂系,46～65,北京:地震出版社。
苏宗正、程新源,1992,1989年大同-阳高地震的地质环境与地震构造,山西地震,(1),19～30。
苏宗正、安卫平、刘 巍等,1994,大同断陷盆地及其大震危险性,山西地震,(4),21～32。
闻学泽,1995,活动断裂地震潜势的定量评估,1～150,北京:地震出版社。
徐锡伟,1989,山西地堑系的新构造活动特征及其形成机制,博士论文,1～242,北京:国家地震局地质研究所。
徐锡伟、车用太、杨主恩等,1991,大同-阳高地震群发震构造模式的讨论,中国地震,7(2),77～85。
徐锡伟、米仓伸之、铃木康弘,1996,山西六棱山北麓晚第四纪不规则断裂作用的地貌学研究,地震地质、18(2),168～180。
徐锡伟,1998,山西高原恒山和六棱山两北麓断裂的运动学基本特征及其地震危险性评估,活动断裂研究6,74～87,北京:地震出版社。
杨景春,1996,大同盆地新构造运动与构造地貌特征,山西地堑系新生代沉积与构造特征,219～234,北京:科学出版社。
TokihikoMatruda,1981,ActivefaultsanddamagingearthquakesinJapanMacroseismiczoningandprecautionfaultzones,EarthquakePredictionAnInternationalReview,MauriceEwingSeries4,Am.GeophysUnion.279～289。
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