Seismic computations on the IBM 3090 Vector

Computerized seismic prospecting is an echo-ranging technique usually targeted at accurate mapping of oil and gas reservoirs. In seismic surveys an impulsive source, often an explosive charge, located at the earth's surface generates elastic waves which propagate in the subsurface; these waves are scattered by the earth's geological discontinuities back to the surface, where an array of receivers registers the reflected signals. The data recorded are then processed in a complex sequence of steps. Among them, seismic migration and stacking velocity estimation represent two characteristic components of the process solving the inverse problem of recovering the structure and the physical parameters of the earth's geologic layers from echo measurements. A complementary tool in relating seismic data to the earth's inhomogeneities is provided by seismic numerical models, which assume a subsurface structure and compute the seismic data which would be collected in a field survey, by solving the direct problem of exploration geophysics. This paper describes a vectorized and parallelized implementation of a two-dimensional seismic elastic model on the IBM 3090 VFVector MUltiprocessor. An implementation of a parallel seismic migration algorithm is then described. The paper also reports performance data for a vector/parallel implementation on the IBM 3090 of some typical seismic velocity estimation algorithms. The three problems chosen are representative of a wide class of geophysical computations, and the results summarized in this paper show their SUitability for efficient implementation on the IBM 3090 Vector MUltiprocessor; combined vector/parallel speedups in the range 15-25 are in fact observed.