新乡-商丘断裂延津至封丘段新构造期构造样式分析

Analysis of Structural Style of Yanjin Fengqiu Section of Xinxiang Shangqiu Fault in Neotectonic Period

新乡-商丘断裂是南华北盆地与渤海湾盆地、鲁西隆起的分界断裂,是一条长期活动的区域性深大断裂。浅层地震勘探与跨断层钻孔联合剖面探测工作已证实该断裂延津至封丘段的最新活动时代为晚更新世,本文通过对典型地震勘探剖面和钻探资料综合分析认为:新乡-商丘断裂延津至封丘段断裂结构复杂,新近纪以来构造样式在不同构造部位有显著差异。延津段在地震勘探剖面上浅部显示为负花状构造;封丘段变化较大,东部在剖面上为多组阶状正断层组合,形成了由断层带控制的构造背斜,平面上表现为NW向排列、走向NNE雁列状断层组合;西部结构单一,自东向西断裂控制的浅部地层变形范围增大,断层带逐步变宽。根据新乡-商丘断裂延津至封丘段剖面上的构造样式与平面上的组合模式,表明该段断裂最新活动具有走滑运动性质。

The Xinxiang-Shangqiu fault is a regional deep fracture of long-term activity marking the boundary between the South North China Basin and Bohai Bay Basin.The latest active age of the Yanjin to Fenqiu fragment of this fault is of late Pleistocene,which is testified by the joint work of shallow seismic exploration and cross-fault borehole detection.On the basis of the typical seismic exploration profiles and drilling data,we concluded that the Yanjin-Fengqiu fragment of the Xinxiang-Shangqiu fault has a very complicated structure.Since the Neogene time,the different tectonic positions of the Yanjin-Fengqiu fragment have quite different tectonic styles.The Yanjin part has a negative flower structure in the seismic exploration profile.However,the Fengqiu part is structurally quite variable.The eastern segment of the Fengqiu part is composed of multiple scalariform normal faults,which form an anticline controlled by a fault belt.These faults are arranged in the NW direction and in echelon with a strike of NNE direction.The western segment is relatively in simple structure,with increasing deformation scale of the shallow strata controlled by the E-W trending fault.The fault zone of the western segment becomes wider from east to the west.According to the tectonic styles and combination patterns of the profile,we concluded that the Yanjin-Fengqiu fragment of the Xinxiang-Shangqiu fault is of strike-slip characteristics.