Seismic migration problems and solutions

Historically, seismic migration has been the practice (science, technology, and craft) of collapsing diffraction events on unmigrated records to point s, thereby moving ("migrating") reflection events to their proper lot, cati ons, creating a true image of structures within the earth. Over the years, the scope of migration has broadened. What began as a structural imaging to ol is evolving into a tool for velocity estimation and attribute analysis, making detailed use of the amplitude and phase information in the migrated image. With its expanded scope, migration has moved from the final step of the seismic acquisition and processing flow to a more central one, with lin ks to both the processes preceding and following it. In this paper, we describe the mechanics of migration (the algorithms) as w ell as some of the problems related to it, such as algorithmic accuracy and efficiency, and velocity estimation. We also describe its relationship wit h other processes, such as seismic modeling. Our approach is tutorial; we a void presenting the finest details of either the migration algorithms thems elves or the problems to which migration is applied. Rather, we focus on pr esenting the problems themselves, in the hope that most geophysicists will be able to gain an appreciation of where this imaging method fits in the la rger problem of searching for hydrocarbons.