A Study Of Active Faults In Zhangjiakou Basin

Active fault is a disaster in the world within the general development of disasters, its frequency and the damage caused by the disaster and the damage caused by the degree of layer is gradually intensified. The investigation of earthquake prediction and the development of engineering construction vigorously promote the study on active faults in recent years.Zhangjiakou basin is situated in the intersection area of the Zhangjiakou-Bohai fault zone and the Shanxi seism tectonic zone. And it is a typical Cenozoic extensional fault-depression basin. There are many active faults in the basin. These faults are controlling the basin development and the evolution. However, the research of active faults in Zhangjiakou basin is very less and mainly to some areas. Therefore, the systematic analysis of active faults, filtering out the quantitative information of active faults, and understanding characteristics of these basins long-term activity, are important in theory and practice.Based on the Analysis and reorganization of the relevant information, detailed field investigations and Shallow seismic exploration, this paper describes geometrical characteristics and tectonic activities of active fault in Zhangjiakou basin. The researched faults include Zhangjiakou fault, Wanquan fault、Ximalin-Shuiquan fault and Yanghe fault.The results showed that:Zhangjiakou fault strikes mainly northwest to east-west, dipping to north, and extends over a length of70kin. As a major geological and geomorphologic boundary, Zhangjiakou fault controls the geotectonic movement in this region, in which its southern side is characterized by Late Quaternary unconsolidated basin deposits, and its northern side is Mesozoic volcano debris and Pre-Mesozoic metamorphic rocks in the form of lower-mountains and hills. Zhangjiakou fault are mainly of high-angle inverse strike-slip fault and partially of normal strike-slip fault. The activity of central segment of Zhangjiakou fault is stronger than other segment. Since late Pleistocene, the average vertical slip rate along single fault is over0.07-0.30mm/a., while the total vertical slip rate overall of entire fault is as high as1.33mm/a.Wanquan fault lie in the northwest of Zhangjiakou basin, and can be divided into northern and southern sections. The fault strikes mainly NNE, dipping to southeast. Wanquan fault are mainly of high-angle normal fault. Since late Middle Pleistocene, the average vertical slip rate along single fault is over0.039-0.05mm/a.Ximalin-Shuiquan fault is located in southwest, and can be divided into four sections. The fault strikes mainly northwest, with high-angle inverse strike-slip fault or normal strike-slip fault characteristics. The latest active time of Ximalin-Shuiquan fault is in late Middle Pleistocene.Yanghe fault is a subsurface fault, and its active time is in Middle Pleistocene. The fault strikes mainly northwest, controled Yanghe river’s flow direction and terrace development. The fault strikes mainly northwest, with high-angle slip fault characteristics.