非均匀应力场下的铲状正断层带位移场和应力场特征

Characteristics of Listric Normal Fault Zone's Displacement and Stress Field in the Inhomogeneous Stress Field

本文利用新的有限元方法研究了铲状正断层带在非均匀应力场下错动引起的位移场和应力场。研究发现:①铲状正断层错动引起的断层面上的最大错距不是发生在地表,而是发生地表下面断层的中部;②地表面最大水平位移和垂直位移都不是发生在地表断层上,而是发生在偏离断层一定距离的地方;③铲状正断层错动会在地表附近产生两个破裂区,一个在地表断层附近,一个在远离断层的上盘地表附近,这两个区与野外观测到的次生正断层区一致;④断层错动的应力降在断层内不是均匀的,最大值也是位于断层中部。

A new finite element method （FEM） in consideration of inhomogeneous stress field is introduced to study the dislocation of a listric normal fault zone＇s displacement and stress fields. New results reveal： （1） the site of maximum slip is at the middle part of the fault, not near the surface. （2） the maximum horizontal and vertical displacements at the ground surface are located at some distance from the fault trace. （3） slip of the fault may result in two failure regions near the ground surface： one close to the surface trace of the fault, and the other within the hanging wall at some distance from the fault; it is in the regions that a succession of normal faults is typically observed in geological examples. 4） The maximum shear stress drop of the fault is also at its middle part.