SECTION MIGRATION, BEFORE STACK, AFTER STACK, OR INBETWEEN *

Section migration after stack has been widely accepted by the industry. From a theoretical point of view, section migration before stack should provide superior results, the improvement warranting the drastically increased cost is not realized in most cases.

There are a number of reasons that explain the discrepancy between actual and theoretically expected quality: Long period statics, refraction of rays, two‐dimensional treatment of an actually three‐dimensional problem.

The section migration package subject to this paper allows

(i) to take refraction into account,

(ii) to discriminate against noise with a variety of statistical and geometrical criteria,

(iii) to adapt processing time to problem complexity by a special process called SEMI‐STACK.

A number of examples will demonstrate the effects of section migration.