Influence of an inhomogeneous stress field and fault-zone thickness on the displacements and stresses induced by normal faulting

Abstract

We used the finite element method (FEM) to simulate the temporal evolution of an inhomogeneous stress field with the aim of investigating the displacement and stress fields induced by slip upon a normal fault zone with a given thickness. The modeling results reveal: 1) the site of maximum slip is along the lower part of the fault, not near the surface, and the locations upon the fault of maximum shear stress drop and maximum slip do not coincide; 2) the maximum horizontal and vertical displacements at the ground surface are located at some distance from the fault trace; and 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. These results differ from those obtained using seismic dislocation theory in semi-infinite space, where the effects of the inhomogeneous stress field and thickness of the fault zone are not considered.