We develop a new imaging condition based on time-shifts
between source and receiver wavefields.
This method is applicable to Kirchhoff, reverse-time and
wave-equation migrations and produces common-image gathers
indicative of velocity errors.
In wave-equation migration, time-shift imaging is
more efficient than space-shift imaging, since it only involves
a simple phase shift prior to the application
of the usual imaging cross-correlation.
Disk storage is also reduced, since the output volume
depends on only one parameter (time-shift ) instead
of three parameters (space-shift ).
We show how this imaging condition can be used to
construct angle-gathers from time-shift gathers.
More research is needed on how to utilize this new imaging condition
for velocity and amplitude analysis.