An endemic problem in reverse-time migration

Abstract

Summary This paper discusses an endemic problem existing in commonly used reverse-time migration (RTM) algorithms, and how to overcome the problem. The problem is illustrated by applying RTM to both synthetic and field datasets. False images appear in the migrated results when strong velocity gradients or complex reflection interfaces are present in the migration velocity model. We have found that the false image is formed by turned or reflected rays that have the same travel-time as the actual wave propagating times. To remove the false images from the migration results, we separate the upgoing and downgoing waves in both source and receiver wavefields, then apply the migration imaging condition to the separated waves. A computationally efficient method can be made to eliminate the false images in RTM.