河北省张家口断裂带的空间展布和第四纪活动特征
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摘要
<正> 一、引言张家口断裂带是北西向张家口—渤海—蓬莱活动构造带西端的一条主要活动断裂,是山西断陷带北段与阴山—燕山断块隆起在该段的分界断裂,它控制着两侧地区的地质发育历史。晚新生代时期有较强烈的活动,构造地貌显示清晰,分段活动性明显。我们通过一些地震工程项目的野外地质地貌调查和年龄测定,并结合前人资料,初步查明了这条断裂带的几何结构、活动性质、最新活动时期和分段性,这对进一步探讨断裂带的地震危险性和评价张家口市区的地震地质稳定性有着十分重要的意义。
The Zhangjiakou fault is one of the major fault zones in the Northwest trending Zhangjiakou-Bohai-Penglai Active Tectonic Belt. It is the boundary between the Shanxi Fault Depression Zone and the Yinshan-Yanshan Block Uplift. Its length is about 52 km, trending N70°-80°W, dipping SW with dip angle≥60°. According to the regional geomorphology, dislocation morphology, and fault profiles outcropped on the ground surface, it is dominated as a normal dip-slip fault. Based on its geometrical distribution, and the difference in activity, it can be divided into 6 segments. Usually they are arranged in right-step en echelon. The Wanquanzheng-Sujiaqiao segment in the west is a newly active one, as an alluvial fan has been offset forming a fault scarplet of 2～3m in height, and the alluvial fan surface has been dated as 17.14±1.46 ka. B. P. The Cuiping' an-Kouli-Dongyiaozi segment is another one relatively active, its latest event has been dated as at 23.7±1.8 ka. B.P. The other segments in the east were mainly active in the mid-Pleistocene to the early stage of late Pleistocene.
The Zhangjiakou fault is one of the major fault zones in the Northwest trending Zhangjiakou-Bohai-Penglai Active Tectonic Belt. It is the boundary between the Shanxi Fault Depression Zone and the Yinshan-Yanshan Block Uplift. Its length is about 52 km, trending N70°-80°W, dipping SW with dip angle≥60°. According to the regional geomorphology, dislocation morphology, and fault profiles outcropped on the ground surface, it is dominated as a normal dip-slip fault. Based on its geometrical distribution, and the difference in activity, it can be divided into 6 segments. Usually they are arranged in right-step en echelon. The Wanquanzheng-Sujiaqiao segment in the west is a newly active one, as an alluvial fan has been offset forming a fault scarplet of 2～3m in height, and the alluvial fan surface has been dated as 17.14±1.46 ka. B. P. The Cuiping' an-Kouli-Dongyiaozi segment is another one relatively active, its latest event has been dated as at 23.7±1.8 ka. B.P. The other segments in the east were mainly active in the mid-Pleistocene to the early stage of late Pleistocene.
引文
① 方仲景等,晋冀北地区的活动断裂及其与地震相关性的研究,85-907-01专题报告,1993。
[1] 河北省地矿局,河北省、北京市、天津市区域地质志,北京:地质出版社,1989。
[2] 徐杰等,华北平原新生代断陷盆地的伸展构造及其地震活动的关系,地震地质.Vol.8,No.1,1986。
[3] 许桂林等,华北盆地北部断裂活动特征及其与地震的关系,华北地震科学,Vol.4,No.1,1986。
[1] 河北省地矿局,河北省、北京市、天津市区域地质志,北京:地质出版社,1989。
[2] 徐杰等,华北平原新生代断陷盆地的伸展构造及其地震活动的关系,地震地质.Vol.8,No.1,1986。
[3] 许桂林等,华北盆地北部断裂活动特征及其与地震的关系,华北地震科学,Vol.4,No.1,1986。
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