Review of tomographic methods

Bernard K. Law, Daniel O. Trad

Classical reflection travel-time tomography can accurately estimate the subsurface velocity; however, the difficulties in picking reflection arrival times on continuous events on CDP stacks and unmigrated gathers make this an undesirable approach. Over the past 30 years, reflection tomography has been extended to estimate other attributes, such as anisotropic parameters and attenuation. Automatic picking of residual moveouts on common image gather in prestack depth migrated domain also improves the picking efficiency. Stereotomography characterizes any reflection event by its two-way traveltime and the apparent slopes or ray parameters in shot and received gathers; hence, does not require picking along continuous reflector. Besides improving the picking efficiency, stereotomography also uses the apparent slopes of coherent reflection events, in addition to the travel-times, in the inversion process. In this study, we review the classical reflection tomography, prestack depth migration tomography, and stereotomography, and to compare the advantages and disadvantages of each method.