基于应力场模拟解释河西务构造带孔店—沙四期断层特征

Fault Characteristics Interpretation of Ek-Es_4 Sedimentary Period in Hexiwu Tectonic Belt through Stress Field Simulation

目前地震、测井等断层解释方法都存在难以解释断层成因机制等缺点,因此选用构造应力场数值模拟从动力学方面解释断层。通过分析河西务构造带断层分布特征及活动特征,发现孔店—沙四期,在构造带南部发育了一系列南东倾向的次级正断层,且断层在平面上呈雁列式展布。为了解释这些次级断层的成因机制,运用Ansys软件对河西务构造带孔店—沙四期的古应力场进行数值模拟,分析应力场的分布特征。结果表明:孔店—沙四期,最小主应力基本为张应力,最小主应力与最大主应力差值在构造带南部较高,控制形成次级断层;构造带南部平面剪应力为左旋,控制断层优势走向为NE向;剖面剪应力为左旋,控制断层优势倾向为SE向。

Some fault interpretation methods are difficult to explain the mechanism of fault,such as seismic,logging and so on,therefore,we choose the tectonic stress field numerical simulation to explain the the dynamics of the fault.Through the analyses of distribution and activity characteristics of the faults in Hexiwu tectonic belt,we find a series of secondary normal faults in the southern part of Hexiwu tectonic belt,which are northeast-trending,southeast-dipping and distribute in echelon form in the plane during Ek-Es4 sedimentary period.In order to explain the formation mechanism of these secondary faults,we simulated the stress field of Hexiwu tectonic belt of Ek-Es4 sedimentary period using Ansys software and analysed the distribution characteristics of stress field.The results show that：the minimum principal is mainly tensile stress;the difference between minimum and maximum principal stress is large in the southern part of the tectonic belt,which control the formation of secondary faults;the strike of the faults is northeast,which is controlled by plane sinistral shear stress;the faults are southeast-dipping,which is controlled by profile sinistral shear stress.