Applying residual phase shifts to wavefield extrapolation

Saleh M. Al-Saleh, Gary F. Margrave

In the generalized phase shift plus interpolation (GPSPI) method, the phase shift extrapolation is used to produce a reference wavefield for each output point using its velocity, and the process is repeated for all output points. This assumes a locally homogenous medium for each extrapolation, and that velocity differences between input and output points are small.

Applying residual phase shifts that account for differences in velocities between input and output points in wavefield extrapolation methods can be helpful in areas that have complicated subsurface structures. In this report, we show how this type of correction can be applied to wavefield extrapolation methods in the space-frequency domain. We use the Marmousi dataset to show the effect of adding this correction. Although no dramatic changes resulted from applying these shifts, some faults and dipping events are better focused and delineated because of them.