An algorithm to solve the inverse problem was implemented, estimating the interval velocity and building seismic models in depth. Based in the paraxial ray theory of seismic optics, the method was applied to seismic data of Majayura project, providing a former model for pre stack depth migration. Traveltimes of reflectors, source and receiver position, used to estimate tha travetiem function, were obtained from cmp gathers and zero offset sections. The diffraction function is estimated from the traveltime function allowing to calculate the interval velocity through focusing of traced rays.