Interpretive Evaluation of Migrated Data

In practice, migration of seismic data requires decision making with regard to:

1. Different migration strategies – 2-D/3-D, post-stack/prestack, and time/depth migrations;
2. different migration algorithms for a given strategy – integral, finite-difference and frequency-wavenumber methods;
3. different parameters for a given algorithm – aperture width, depth-step size, stretch factor;
4. the input data – profile length, noise content, spatial aliasing and boundary effects;
5. and finally, migration velocities – the weak link between the seismic method and the subsurface geology that the former tries to image.

The seismic interpreter, whose main role is to infer subsurface geology from the migrated data, normally should not be burdened with the decisions concerning the above factors. Fortunately, migration results often are self-evident; a feature considered geologically implausible on a migrated section can be associated with one or more of the above factors. Based on large number of field data cases, I will discuss each of these factors and provide some generally applicable guidelines for migration that an interpreter can invoke in practice.