Abstract
An equation which represents the crack propagation is obtained by approximating the wave equation and the boundary conditions in the neighborhood of the dislocation surface. The problem of crack propagation with an unsteady finite rupture velocity is solved with the aid of this model and the computation is carried out by using the finite difference method. The proposed model takes the rupture propagation as the diffusive phenomena of the inhomogeneous initial stress field. It is clarified in this paper that the most important focal parameters for the dynamical process of fault motion are the effective stress (defined as the static frictional stress minus the sliding frictional stress) and the fracture strength (defined as the static frictional stress minus the initial stress). The former accelerates the fault motion and the latter decelerates it. All the rupture phenomena can be interpreted by the relative magnitude between these stresses. The importance of both stresses is not ascertained until the inhomogeneous initial stress field is introduced.
