Differential Semblance Wavefield Tomography Using Extended Images

Wavefield tomography can be formulated based on extended images constructed at discrete locations in the subsurface, i.e. by analysis of extended common-image-point gathers. Such gathers can be built at locations that conform to the geologic structure, thus achieving optimal sampling of the image. The extended CIPs indicate velocity error by defocusing from the origin of the space- and time-lag domain. We can formulate an objective function based on this information by penalizing the image departure from its ideal shape. Such penalty resembles the process used for differential semblance optimization on more conventional common-image-gathers and is characterized by similar robustness and simplicity.