Two techniques for the absorption of elastic waves using an artificial transition layer

The paper deals with the treatment of artificial boundaries within the framework of characteristic-based finite difference methods for the propagation of elastic waves inlarge or infinite solids. In order to restrict the computational domain mainly to the area of technical interest and to suppress non-physical reflections on its boundary, an absorbing transition layer adjacent to this kernel area is used. The transition layer is designed to match the material properties in the kernel area so that outgoing waves can propagate across the interface between the kernel area and the transition layer without reflection and are almost absorbed in that layer. Two different techniques are adopted for the transition layer. One gradually reduces the amplitude of waves in the transition layer, and the other modifies the wave speeds there. Together with dissipative finite difference schemes, both techniques show numerical efficiency. Numerical examples including cracked media, where plane wave fronts: and curved wave fronts (e.g. radiating from the crack tip) occur, are presented.