f Migration velocity analysis using common offset depth migration

In geological areas with sufficiently strong vertical and lateral velocity gradients, it is necessary to use pre-stack depth migration in order to obtain an optimum sub surface image from seismic data. There are several means of performing pre-stack depth migration but they all require an accurate velocity-depth model as input . Errors in the model lead to poor imaging of the structure and allo mispositioning of the data, both vertically and laterally . Obtaining an accurate model prior to performing the migration is usually the most difficult part of pre-stack depth migration .