A traditional imaging condition for shot-record
migration, often referred-to as imaging condition
consists of time cross-correlation at every image location
between the source and receiver wavefields,
followed by image extraction at zero time:
where the symbol denotes cross-correlation in time.
is a vector describing the locations of image points,
are source and receiver wavefields respectively, and
denotes a migrated image.
A final image is obtained by summation over shots.