INCORPORATION OF ABSORBING BOUNDARY-CONDITIONS INTO ACOUSTIC AND ELASTIC-WAVE PROPAGATION PROBLEMS SOLVED BY SPECTRAL TIME-MARCHING

The focus of this paper is a detailed description of the incorporation of absorbing boundary conditions in the symbolic solution of the two- dimensional elastic wave equation. This symbolic solution forms the ba sis for the spectral time-marching technique, which is also described. Application of the absorbing boundary conditions necessitates the emp loyment of a spatial spectral discretization, yielding an algorithm wh ose accuracy is balanced in time and space. To illustrate the usefulne ss of the method, a numerical example of horizontally polarized shear waves is presented. The snapshots amply demonstrate how well the numer ical absorbing condition works, a consequence of Chebyshev nodal clust ering. The kernel operation of this time-stepping algorithm is matrix multiplication, efficiently implemented on existing supercomputers. Ex ecution time for the numerical example, on the VPX240/10, was a sustai ned processing rate of 650 M-FLOPS or 37% of the achievable peak perfo rmance of 1.76 G-FLOPS. Copyright (C) 1996 Published by Elsevier Scien ce Limited