冀中坳陷东北部河西务断裂深浅构造特征

浅层高分辨率地震探测揭示,河西务断裂在近地表为倾角70°—75°的高角度正断层,断裂由1条主干断裂及1条次级断裂构成。主干断裂上断点埋深170 m左右,活动时代为中更新世晚期。石油深地震探测结果和大地电磁测深资料分析结果显示,断层上陡下缓,呈铲形,两侧地层角度不整合,扩展向斜、褶皱和伴生断裂发育,断裂切割较深,在38 km左右深度与大兴断裂交汇向下延伸,进入上地幔,断裂的下盘存在壳内高导体(层)。结合精定位小震的分布以及华北地区地震孕育发生的特点认为,河西务断裂存在中强地震发生的构造背景。

Deep and shallow structural characteristics of Hexiwu fault in northeastern Jizhong depression

Shallow high resolution seismic detection shows that the Hexiwu fault in the near surface is a normal fault with a dip angle of 70 to 75 degrees, which is composed of a main fault and a secondary fault. The breakpoint of the main fault is 170 m or so and the active age was belonged to the late Pleistocene. Combined with deep seismic data and magnetotelluric data, it is found that the fault is characteristic of abrupt and listric shape with unconformable angle of the two sides, expansion of syncline, folds and associated faults which is deeply cut through Moho about 38 km that extended to Daxing fault and converged downward into the basement to the upper mantle. In the footwall of the fracture, there is a high conductor (layer) in the shell. Combined with fine location of small earthquakes and the characteristics of earthquake preparation in North China, there is a tectonic background of the occurrence of medium-strong earthquakes in Hexiwu fault.