Velocity backprojection from image differencing

Ray-based reflection tomography has become widely used as a tool for updating velocity models in depth imaging. Historically, development of ray-based tomography for depth imaging followed two separate methodologies. Early ray-based tomography was based on differences in traveltime observed between modeled data and actual seismic data (Bishop et al, 1983). As technology for imaging in complex areas progressed, however, it became more difficult to obtain reliable time differences on input data, and hence an alternative methodology based on residual moveout on migrated offset gathers was developed (Stork, 1992).