Steep‐dip v(z) imaging from an ensemble of Stolt‐like migrations

Stolt migration is often performed with many dif-ferent velocities, creating a cube (or ensemble) of migrated constant-velocity sections. With this ensem-ble, an interpreter can quickly, even interactively, carve out a single, variable-velocity time migration. Unfortunately, the variable-velocity section obtained in this way cannot image steep dips correctly. Phase-shift (i. e., Gazdag) migration accurately im-ages reflections from steep interfaces where velocity varies with depth. However, it is computationally slow compared to Stolt's f-k migration, its constant-veloc-ity counterpart. Similarities between the Gazdag and Stolt methods allow a mapping between the two to be derived. This new mapping, which replaces the constant-velocity Stolt mapping, defines a new Stolt-like migration. Stolt-like migration can then be performed to create an ensemble of migrated data, from which a Gazdag-equivalent migration can be carved. All dips can be imaged properly, even where velocity varies signifi-cantly with depth, while the advantages of working with the ensemble of migrated sections are preserved.