Velocity Inversion Using a Stratified Reference

Résumé du livre

The purpose of this work is to present an inversion algorithm for backscattered stacked seismic data which will reconstruct the velocity profile in realistic earth conditions. The basic approach follows that of the original Cohen and Bleistein paper in that high frequency asymptotics and perturbation methods are used. However, in the original paper the perturbation was relative to a constant reference speed, whereas the current work uses a reference speed which may vary with depth. This greatly enhances the validity of the perturbation assumption and hence the inversion results. On the other hand, the new algorithm enjoys the same economies and stability properties of the original algorithm, making it very competitive with current migration schemes. Four major assumptions are made: (i) the acoustic wave equation is an adequate model, (2) stacked data has amplitude information worth preserving fairly accurately, (3) the actual reflectivity coefficients can be adequately modeled as perturbations from a continuous reference velocity which depends only on the depth variable, and (4) the subsurface can be adequately modeled as a series of layers with jump discontinuities in the velocity (or impedance) at these layers.