OPTIMUM IMAGE

The main purpose of migration is to obtain an accurate image of the subsurface. This image is used to interpret the structure and identify the composition of the subsurface. We usually consider the image obtained by migration as a map of the averaged reflection coefficients. For use in a structural interpretation, some large values along the reflector to increase the contrast of the reflector image from background noise would be sufficient. For the identification of the subsurface rock properties, however, the image must be clarified in terms of the relation to the true reflection coefficient.

The reflection coefficient is a function of the angle of incidence at a reflector. In order to describe a reflector completely, therefore, the image should be multi-valued, with each image determined by the angle-dependent reflection coefficient. Or it can be represented by a single value which characterizes the reflector, such as the maximum reflection coefficient, the reflection coefficient of the normal incident wave, or the integral of the reflection coefficient along some angle.