Imaging land seismic data is wrought with many technical challenges that arise during different stages of seismic investigation: acquisition (e.g. irregular geometry), preprocessing (e.g. ground-roll suppression, statics), velocity estimation (e.g. near-surface complexity) and migration (e.g. rugged topography, uncertain velocities). Each of these complicating factors needs addressing before satisfactory final images are generated. Given the completion of each pre-migration processing step, one may choose from a variety of migration techniques; however, velocity profiles and geologic structures often are sufficiently complex to warrant wave-equation imaging. A caveat, though, is that wave-equation migration (WEM) is usually implemented with regularly sampled data on Cartesian meshes. Hence, conventional WEM from topography usually requires data regularization prior to migration.
Topographic data regularization approaches often include pre-migration datuming using statics corrections. These basic processes use vertical time-shifting of the wavefield to estimate the data recorded on a flat datum above or below the true acquisition surface. Standard migration techniques (e.g. wave-equation or Kirchhoff) may then be applied directly to the regularized dataset. However, the vertical wavefield propagation assumption usually is not satisfied in areas characterized by fast near-surface velocities and strong velocity gradients (e.g. in the Canadian Rocky Mountain Foothills) due to limited accuracy at propagation angles that deviate significantly from vertical. Hence, more advanced techniques able to incorporate topography are needed. A short and not exhaustive list of such methods (e.g. using more kinematically correct Kirchhoff operators Bevc (1997)) is presented in Shragge and Sava (2004).
In general, most wave-equation processing solutions to topographic data irregularity use a strategy of forcing data to conform to Cartesian geometry. The converse of this situation is to tailor wave-equation migration implementation to coordinate system meshes defined by the acquisition geometry. Shragge and Sava (2004), following the latter strategy, extend wave-equation migration to ``topographic coordinate systems'' conformal to acquisition topography. Although Shragge and Sava (2004) applied this approach to synthetic 2D data, they neither tested the algorithm on field data nor compared it to more conventional imaging from standard topography approaches (e.g. Kirchhoff migration). This paper addresses these issues with imaging experiments using the Husky 2D land dataset acquired in the Canadian Rocky Mountain Foothills.