Abstract: Method of determining the velocity V and anellipticity ? parameters for processing seismic traces in a common midpoint (CMP) gather comprising:—a preliminary step to define a plurality of nodes (dtn, ?o), for each node (dtn, ?o) defined in the preliminary step, the following steps:—for static NMO correction of traces in the CMP gather as a function of the values of the said parameters dtn and ?o at the node considered, and calculation of the semblance function associated with the said NMO correction for the node considered; and—for each picked time to, a step including determination of the maximum semblance node (dtn (to), ?o (to)),—and a final step to convert the dtn (to) and ?o (to) parameters, so as to obtain the velocity to) and anellepticity ? (to) laws.