The deformation of the ground around surface faults

Abstract A rectangular dislocation surface (i.e., a surface across which there is a discontinuity in the displacement vector) is used as a model of a vertical transcurrent fault. The results of Steketee (1958a) are employed to derive, in analytical form, the displacement field throughout a semi-infinite elastic medium due to such a dislocation. In particular, the displacements of the surface of the medium are calculated in some detail, and contour maps of the various components are given for two representative cases. The solution to the limiting case of a fault of infinite length is also included. Methods are then discussed for the determination of the depth of a surface fault from measurements of the deformation of the ground produced by it, and these are applied to the faults associated with the Tango and North Idu earthquakes, and to the San Andreas fault. In each of these cases, the general features of the crustal deformations agree well with the predictions of the theory, and it is concluded that dislocation theory provides a good description of the effects of fracture in the earth's crust.