Tutorial: migration imaging conditions

Migration of seismic data is the process that attempts to build an image of the Earth’s interior from recorded field data, by repositioning these data into their ‘true’ geological position in the subsurface, using various numerical approximations of either a wave-theoretical or ray-theoretical description of the propagation of sound waves in the subsurface. This migration can be described as being performed in a number of stages, both for ray and wave-extrapolation based methods. The final stage of the migration process is that which forms the image, via what is known as an imaging condition. In this tutorial, I will outline the various methods involved in forming imaging conditions, primarily for the case of wave-extrapolation methods, and describe some of the techniques used to build gathers of pre-stack-migrated data for use in post-migration velocity analysis.