ANISOTROPIC MIGRATION OF COINCIDENT VSP AND CROSS-HOLE SEISMIC-REFLECTION SURVEYS

Seismic depth migration may result in false reflector positioning and destructive interference when an incorrect velocity field is used to c onvert from time to depth. The assumption of isotropy to describe anis otropic rocks is one major source of error in the velocity model, alth ough individual survey images may not be impaired by such an approxima tion. When different survey types such as VSP and cross-hole reflectio n seismics have coincident illumination of the subsurface, it is impor tant not only to produce consistent images upon depth migration, but a lso to determine a consistent velocity model. Using real data sets as examples, both objectives are successfully achieved when anisotropy is incorporated into the velocity model.