Imaging and coherency in complex structures

In complex structures, more than one pair of rays may connect a source and receiver via a scattering point. Whenever many such pairs of rays exist and have the same two-way traveltime, an inherent ambiguity appears in the inverse scattering process. Unless a simple ray geometric condition is met, the migrated section will contain images that need not belong to the actual reflectivity field. The geometric requirement relates to the acquisition geometry, and it is almost always satisfied when the sources and receivers both cover an area. Even if the geometric requirment is satisfied for the acquisition geometry, it may not be so for single source experiments (different acquisition geometry) - consequently coherency panels may not be flat, even if one migrates with the exact background velocity.