The pseudospectral method: Comparisons with finite differences for the elastic wave equation

The pseudospectral (or Fourier) method has been used recently by several investigators for forward seismic modeling. The method is introduced here in two different ways: as a limit of finite differences of increasing orders, and by trigonometric interpolation. An argument based on spectral analysis of a model equation shows that the pseudospectral method (for the accuracies and integration times typical of forward elastic seismic modeling) may require, in each space dimension, as little as a quarter the number of grid points compared to a fourth-order finite-difference scheme and one-sixteenth the number of points as a second-order finite-difference scheme. For the total number of points in two dimensions, these factors become l/16 and l/256, respectively; in three dimensions, they become l/64 and 114 096, repectively In a series of test calculations on the two-dimensional elastic wave equation, only minor degradations are found in cases with variable coefficients and discontinuous interfaces.