Downward Continuation of Common Midpoint Gathers by Transformation into Snell Trace Coordinates
, by Rick Ottolini
This report studies a gather-only subset of the theory developed by Ottolini in "Migration of Radial Trace Sections" (SEP-20). First, Snell trace coordinates are distinguished from radial trace coordinates as incorporating a depth variable velocity structure. Next, the downward continuation algorithm is shown to be a p-dependent time shift in Snell trace coordinates. Finally, synthetic and real data examples demonstrate the workability of this method. These examples are compared to radial trace and the wave-equation based phase shift downward continuation methods. The Snell trace coordinate method has fewer artifacts than the wave equation scheme.
STANFORD