Chapter 3 focus in the analysis and interpretation for the dimensions of the prestack image that is obtained through wave-equation migration. I presented a method to accurately transform-subsurface-offset domain CIGs into angle-domain CIGs, for converted-wave data. This method requires the information along the midpoint axis and the velocity ratio.
For the converted-mode case, the angle representation of the image is the average of the sum for the P-incidence angle and the S-reflection angle. The correct PS-ADCIGs can also be mapped into two different angle axes, each one representing the the P-incidence angle and the other representing the S-reflection angle. This mapping might yield useful information for velocity updates for the two different velocity models.
The real data results illustrate the application for the method introduced in this chapter. Because of the strong difference between the residual moveout present in the PZ-ADCIGs and the true PS-ADCIGs, the S-velocity model was updated to satisfactorily produce PZ and PS images with similar geological interpretaions.