A method for obtaining a volumetric image of a geological structure in the subsoil includes generating a plurality of seismic waves by plural seismic sources, acquiring signals or traces obtained by processing the seismic waves reflected by the geological structure for creating a seismic record or shot gather for the activation position of each seismic source, migrating, through a numerical processing, each shot gather to create a respective partial volumetric image of the geological structure, summing the single partial volumetric images to obtain the overall volumetric image of the geological structure, the summing of the single partial volumetric images being obtained by grouping the seismic sources into groups, grouping the groups of seismic sources into super-groups, and effecting N migrations for each super-group.