3-D pseudospectral prestack reverse-time migration with application to reverse-VSP data

A 3-D acoustic prestack reverse-time migration algorithm based on a pseudo-spectral wavefield extrapolator is developed, implemented and tested. The computation used very-large mixed-radix multiple-processor 3-D Fourier transforms for fast, accurate, stable solution of the full 3-D scalar wave equation. Implementation is on a CRAY-2. The algorithm is applied to synthetic reverse-VSP common-source seismic data. Implicit static corrections may be used for data from surface recording arrays deployed on large elevation changes and/or near-surface velocity variations. Short and long-wavelength source and receiver statics can be accurately and simultaneously corrected during 3-D prestack migration. Examples include imaging of salt and subsalt structures from synthetic wide-aperture seismic data for sources located in a deviated borehole. The 3-D nature of the recorded wavefield requires full 3-D depth migration; 2-D processing of the data produces unrecognizable images dominantly by artifacts.