断展褶皱要素对隐伏滑脱层深度及几何样式的约束:数学分析及其在重庆地区薄皮构造中的应用

根据平衡地质剖面原理,在前人建立的断展褶皱数学模型基础上,进一步推导出断展褶皱要素组合对隐伏滑脱层发育深度和几何样式的限定。需要给定的参数组合包括:断展褶皱后翼倾角2θ、翼间角γ、背斜的构造高度h、背斜的宽度LAB、断端点T以上地层厚度h0。这些参数均可由野外实测或地震剖面解释中给定。由这些参数可以推导出:断坡的倾角α、断坡的顶点T到断层滑距开始降低的点P的距离LTP、地层的压缩量f0、隐伏滑脱层的深度h’。将此推导过程用VC++编程软件ZB1.0加以实现。根据地震剖面的解释及地表资料整理结果,把上述演算结果应用于重庆方斗山地区的茨竹亚背斜的2个剖面中,计算出隐伏滑脱层的深度分别为8.10~8.63 km,证明茨竹亚背斜隐伏主滑脱层发育于寒武系底部。滑脱断层断坡倾角为29°~45,°属于中等倾角。这一研究成果既可在理论上定量计算隐伏滑脱层样式和深度,又能指导对潜伏构造的勘探实践。

Constraints the Depth and Geometry of the Subsurface Detachment Fault from Parameters of Propagation Anticline: Geometrical Model and It's Applied to Thin-skinned Thrust in Chongqing Area, South China

A geometrical model,which utilizes an assemblage of parameters of propagation anticline to constraint the depth and geometry of the blind detachment fault,is figured in this paper based on both balanced geosection principles and previous studies.The parameters measured from anticline in this model include backlimb angle,interlimb angle,the height of anticline,the width of the anticline and the thickness of the layer upwards point fault tip.The calculation could be practiced using software ZB1.0,which was programmed in VC++,and gives results of the detachment fault,including ramp dip angle,fault-parallel distance,strata draught and the deepth of flat.Parameters of anticline,which are from seismic and geological sections of the Cizhuya propagation anticline,respectively,give the consistent depth and dip angle of detachment fault at 8.10-8.63 km and 29°-45°.The depth indicates the detachment fault along the bottom of Cambrian,while the dip angle suggests a medium dip for the fault ramp.The results are also consistent with the regional geological estimation,and thus proved that the geometrical model is practicable to petroleum exploration and subsurface structures in this area.