Model 4: Migration
In this chapter, we develop tools that migrate data and that display migrated data.
In Section 9.2.2, we will use migration program sustolt. Here, we examine its parameters (except verbose and tmpdir).
The first two parameters, cdpmin and cdpmax, are required and have no default values. They allow us to apply DMO to a specified range of input CDPs. We will always set these minimum and maximum values to include all our input CDPs. In other words, we will always let sustolt apply DMO to all input CDPs. DMO, dip moveout correction, is NMO corrected for dipping beds in prestack data. Because we are migrating stacked traces, range refers to the CDPs that will be migrated.
The third parameter, dxcdp, is required and has no default value. To determine the CDP bin distance of Model 4, we created a stacking chart similar to the one shown in Sheriff (2002). Figure 9.1 is a subset of the acquisition geometry described in Section 6.3, but it includes enough geometry to let us calculate the CDP bin distance. Model 4 was acquired with a split-spread line of 60 receivers, receivers spaced 50 meters apart, with line moves 50 meters between shots. The split-spread line of Figure 9.1 has only 10 receivers, but receiver spacing and line movement are the same as for Model 4. The diagonal line of Common Midpoint Direction cuts the diagonal of 50 meter x 50 meter boxes. Therefore,
Since we will migrate stacked data, we will ignore parameter noffmix.