Comprehensive Survey and Study on the Activity of the Hexiwu Fault in Langfang Area, Hebei Province
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摘要: 河西务断裂为河西务构造带的东缘断裂,总体走向北东,倾向南东,向北延伸与廊固凹陷内的横向断层(桐柏断裂)小角度相接,向南延伸与牛东断裂相接,为廊固凹陷与武清凹陷的分界断裂,隐伏于冀中凹陷覆盖层之下。本文通过浅层地震勘探和钻孔联合剖面探测,结合年代样品测试,对河西务断裂的活动性和滑动速率进行了综合研究,揭示断裂上断点埋深约150m或以浅,第四系底界面的垂直错距为20—45m,断裂的最新活动时代为晚更新世早期,晚更新世以来的平均垂直滑动速率为0.03mm/a,中更新世晚期以来的平均垂直滑动速率为0.11mm/a。Abstract: The Hexiwu fault is the eastern margin fault of Hexiwu tectonic belt, and is concealed under the cover of the Jizhong depression. We have conducted comprehensive survey and research on Hexiwu fault through petroleum drilling data analysis, shallow seismic exploration, composite drilling section and faulting age determination. The results showed that Hexiwu fault is an extensional detachment fault, which is composed of a main fault dipping to southeast and many secondary faults dipping to SE/NW. The width of the fault zone at surface is about 2—4km, where the surface projection of the breakpoint displays the nearly parallel distribution of primary and secondary faults. In the deep part of the fault zone, the fault is in the form of a ladder eastward slipping, and the second fault has a tendency to attribute to the main fault. The main fault activity in the fault zone is stronger than the secondary faults, generally strikes NE, trend SE, dipping to 50°—65°, with breakpoint on the buried depth of about 150m. The most recent faulting activity is in the early late Pleistocene and the late Pleistocene with sliding rate of 0.03mm/a.
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图 2 LF-511、LF-313和WA-623人工地震地质解释剖面(据赵红格,2000)
Figure 2. LF-511, LF-313 and WA-623 seismic interpretation sections (Zhao Hongge, 2000)
表 1 冶炼厂场地各孔分段深度表(单位:m)
Table 1. Depth of holes in the site of metallurgical plant (Unit: m)
地层时代 钻孔编号 LY-3 LY-1 LY-4 LY-2 全新统(Q4) 28.2 27.2 27.8 27.4 上更新统(Q3) 169.1 168.5 172.6 172.9 中更新统(Q2,未见底) 241.1 241.0 243.9 244.5 -
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