银川地堑地壳挤压应力场:深地震反射剖面

银川地堑位于南北地震带北段,地质结构复杂,活动构造发育.为了调查银川地堑的构造特征及断裂分布情况,布设了NW向跨银川地堑的深地震反射剖面,首次获得银川地堑地壳的精细结构.结果表明,银川地堑具有典型的拉张-挤压型沉积盆地特征,上地壳反射连续性好,层位丰富,能量强,断裂发育.下地壳和莫霍面记录了挤压与拉张的发展过程.奠霍面...

The compressive stress field Of Yinchuan garben: Deep seismic reflection profile

Yinchuan graben, located in the northern section of North-South seismic zone, has complex geological structure and active tectonics. In order to investigate the structural characteristics of Yinchuan graben and fault distribution, we laid the NW-trending deep seismic reflection profiles across the Yinchuan graben which revealed the fine crust structure of Yinchuan graben for the first time. The results show the typical characteristics of tension-compression sedimentary basin of the Yinchuan garben and the reflections of the upper crust have the characteristics of good continuity, rich horizon, strong energy, and abundant normal faults. The lower crust and Moho recorded the development process of extension and compression of the basin. Moho appears as an intensive reflection layer, which is laterally discontinuous, changes significantly in depth with the deepest part in the middle of the section. The western lower crust in the sections shows bent features and contains the reflection characteristics of "hyacinth bean". This may be related to the compressional effects on Yinchuan graben since the Late Triassic. The eastern lower crust and Moho reflection in the section are staggered by Yellow River fault belt, and the Moho dislocation occurs on both sides of the fault, indicating the strike-slipping and extensional effect of the Yellow River fault. The deep seismic reflection profiles also reveal that the fault belt in eastern piedmont of Helanshan and the Yellow River fault belt are two major deep faults to control the basin. The fault belt in eastern piedmont of Helanshan cut through the interface of the upper-lower crust into the lower crust. The Yellow River fault belt is a huge intra-continental strike-slip fault, and the shallow part appears as a typical flower structure, and the deep part appears as bundle-like tilt reflection. The Yellow River fault belt extends to the lower crust, cutting through the Moho. The shape of thrust-nappe belt of the graben and the crust in the middle and western profile shows that this graben is subject to the action of the regional compressive stress field from the basin to the substrate. The direction of the regional compressive stress field is southwest. In this paper, we discuss the cause of the M8.0 earthquake happened at Yinchuan in 1739 and the good hydrocarbon potential in Yinchuan graben.