The effect of irregular acquisition topography is that it distorts seismic data. This is a serious problem in mountainous regions where there is extreme topographic relief along seismic lines. Wave equation datuming provides a useful method of transforming data to a planar datum and determining the near surface velocity structure. This eliminates the distortion caused by the topography and allows standard processing methods such as velocity analysis, DMO, and migration to be efficiently applied Bevc (1992b).
Several authors have shown that wave equation datuming is better than statics for continuing data through known velocity structures Reshef (1991); Shtivelman and Canning (1988); Wiggins (1984). These authors do not discuss the determination of the velocity to be used in the datuming process. In order for these methods to work, the near surface velocity must be known. I address the more general situation for which the near surface velocity structure is unknown.
When the near surface velocity is unknown there are different ways to proceed depending on the nature of the seismic data. One approach is to upward continue the data to some planar datum above the topography with a fictitious extrapolation velocity. This should unravel the distortions caused by the irregular acquisition topography and allow standard imaging techniques to be applied to the data Bevc (1992a,b); Payne and Marcoux (1992). Another approach is to downward continue the data through the near surface with many estimates of the actual velocity. When the correct velocity is used, wave based processing procedures such as velocity analysis are optimized. This concept forms the basis for a near surface velocity inversion scheme.
Both these schemes are computationally intensive, especially the second one which requires multiple applications of the datuming algorithm. To tackle such problems I developed an efficient data parallel Kirchhoff datuming algorithm on the Connection Machine. I describe the implementation of the algorithm and apply it to prestack land data from the Wyoming overthrust belt.