On the Influence of Offset in Plane-Wave Migration

This paper considers the influence of offset on plane-wave illumination and migration for seismic data. It is shown that, for a single offset, complete illumination and migration can only be achieved using plane waves encompassing all angles of incidence. By contrast, when a full range of offsets is used, it is possible in principle to illuminate and image the subsurface using only two plane waves. These results are confirmed using synthetic data. The number of plane waves required for plane-wave migration has a direct impact on computational cost. In practice, offset limitations, as well as other considerations, make it unrealistic to expect successful imaging using as few as two plane waves. However, the theory does support imaging with fewer plane waves than might otherwise be thought necessary. This is illustrated by a marine data example for which a good migrated image was obtained using only six plane waves.