MIGRATION ALGORITHM

The migration algorithm used is a variation of the split-step method Stoffa et al. (1990). A brief description of the basic algorithm can be found in this report Gratwick (2001). Our image gathers are a function of offset ray parameter, P_h, which is given by equation (1):

$$P_h \; = \; \frac{2 \sin \theta \cos \phi}{V(z,{\bf m})} \;,$$ (1)

where $\theta$ is the incidence angle, $\phi$ is the geologic dip, and $V(z,{\bf m})$ is the local interval velocity function as a function of midpoint.

The flow of the migration and the factors which affect amplitude preservation are outlined in Figure 1. All schematic image gathers are from a hypothetically flat, constant amplitude reflector. The expected image gather after true amplitude migration is seen in the upper-left corner of Figure 1.