Abstract: An objective function is disclosed that extracts the velocity error information directly in the image domain without computing common-image gathers. Because of the dimensionality of the problem, gradient-based methods (such as the conjugate-gradient algorithm) are used in the optimization procedure. In order to include the full complexity of the wavefield in the velocity estimation algorithm, a two-way (as opposed to one-way) wave operator is considered, where the imaging operator is not linearized with respect to the model parameters (as in linearized wave-equation migration velocity analysis), and the gradient of the objective function is determined using the adjoint-state method. The velocity estimation methodology is illustrated with a few synthetic examples.

Abstract: 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.

Abstract: An objective function is disclosed that extracts the velocity error information directly in the image domain without computing common-image gathers. Because of the dimensionality of the problem, gradient-based methods (such as the conjugate-gradient algorithm) are used in the optimization procedure. In order to include the full complexity of the wavefield in the velocity estimation algorithm, a two-way (as opposed to one-way) wave operator is considered, where the imaging operator is not linearized with respect to the model parameters (as in linearized wave-equation migration velocity analysis), and the gradient of the objective function is determined using the adjoint-state method. The velocity estimation methodology is illustrated with a few synthetic examples.

Abstract: 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.