2-D PSEUDOSPECTRAL VISCOACOUSTIC MODELING IN A DISTRIBUTED-MEMORY MULTIPROCESSOR COMPUTER

Two pseudo-spectral implementations of 2-D viscoacoustic modeling are developed in a distributed-memory multi-processor computing environmen t. The first involves simultaneous computation of the response of one model to many source locations and, as it requires no interprocessor c ommunication, is perfectly parallel. The second involves computation o f the response, to one source, of a large model that is distributed ac ross all processors. In the latter, local rather than global, Fourier transforms are used to minimize interprocessor communication and to el iminate the need for matrix transposition. In both algorithms, absorbi ng boundaries are defined as zones of decreased Q as part of the model , and so require no extra computation. An empirical method of determin ing sets of relaxation times for a broad range of Q values eliminates the need for iterative fitting of Q-frequency curves.