OFFSET CONTINUATION IN THEORY AND PRACTICE *

A bstract Offset continuation is a technique that was recently proposed for the dip moveout correction. This correction can be carried out in the time‐wavenumber domain using a proper partial differential equation that links sections with different offset. It has been shown that a single spike in a common‐offset section—corresponds to a semi‐elliptically shaped reflector with foci located at the source and receiver in the section migrated after dip moveout correction. The sections that result after offset continuation, stack, and migration are thus a superposition not only of semicircles, but also of semi‐ellipses with different lengths of axes. This effect smears the migration alias‐noise which, without offset continuation, would appear as migration circles not close enough together to interfere destructively. Offset continuation can improve the quality of seismic sections in several ways: —the velocity analyses are more readable, less dispersed and dip independent; diffraction tails arrive with the same normal moveout velocity as the apex and thus diffraction‐noise can be “stacked out”; —noise produced by aliasing in the migrated section is reduced. In this paper we give a practical and conceptual interpretation of the offset continuation method, with a generalization to three‐dimensional volumes of data. A critical examination of several synthetic and field data examples shows the actual possibilities and advantages of offset continuation.