ARTICLES

Flooding the topography

By Dimitri Bevc

Wave-equation datuming overcomes some of the problems that seismic data recorded on rugged surface topography present to routine image processing. The main problems are that (1) standard, optimized migration and processing algorithms assume data are recorded on a flat surface, and that (2) the static correction routinely applied to compensate for topography is inaccurate for waves that do not propagate vertically. Wave-based processes such as stacking, dip moveout correction, normal moveout correction, velocity analysis and migration after static shift can be severely affected by the non-hyperbolic character of the reflections.

To alleviate these problems, I apply wave-equation datuming early in the processing flow to upward continue the data to a flat datum, above the highest topography. This is what I refer to as ``flooding the topography''. This approach does not require a detailed a priori knowledge of the near-surface velocity, and it streamlines subsequent processing because the data are regridded onto a regularly sampled datum. Wave-equation datuming unravels the distortions caused by rugged topography, and unlike the static shift method, it does not adversely effect subsequent wave-based processing. The image obtained after wave-equation datuming exhibits better reflector continuity and more accurately represents the true structural image than the image obtained after static shift.

Geophysics, vol. 62, No. 5, (September-October, 1997) 1558-1569.