A NUMERICAL LABORATORY FOR SIMULATION AND VISUALIZATION OF SEISMIC WAVE-FIELDS

Computational seismic modelling (CSM) plays an important role in the g eophysical industry as an established aid to seismic interpreters. Num erical solution of the elastic wave equations has proved to be a very important tool for geophysicists in both forward modelling and migrati on. Among the techniques generally used in CSM, we consider the finite -element method (FEM) and investigate its computational and visualizat ion requirements. The CSMFEM program, designed for this purpose and de veloped on an IBM 3090 computer with vector facility, is described in detail. It constitutes a numerical laboratory for performing computer experiments. Two Newmark type algorithms for time integration are comp ared with other time integration schemes, and both direct and iterativ e methods for solving the corresponding large sparse system of linear algebraic equations are analysed. Several numerical experiments to sim ulate seismic energy propagation through heterogeneous media are perfo rmed. Synthetics in the form of common shot gathers, vertical seismic profiles and snapshots are suitably displayed, since with the large am ounts of data obtained from CSM research, methods for visualization of the computed results must be developed. The FEM is compared with othe r numerical tools, such as finite-difference and pseudo-spectral metho ds.