A method for use in seismic exploration includes: obtaining a diving wave illumination image of a subterranean region from a set of seismic data representative of the subterranean region using a selected acquisition geometry; clipping an inverse of the diving wave illumination image to a range of values; and performing a weighted full-waveform inversion. The weighted full-waveform inversion further includes: weighting a full-waveform inversion gradient with the clipped inverse of the diving wave illumination image; and performing the full-waveform inversion using the weighted gradient.

A technique for estimating a depth of investigation of a seismic survey includes in various aspects a method and an apparatus. The method is for use in seismic exploration and includes: forward modeling on a subsurface attribute model of a subterranean region to generate a set of low frequency seismic data, the subsurface attribute model being generated from data representative of the subterranean region; performing a reverse time migration on the low frequency seismic data to obtain a plurality of gathers with large opening angles; stacking the gathers to yield a diving wave illumination image; and estimating a full-waveform inversion depth of investigation from the diving wave illumination image. The apparatus may include a computing apparatus programmed to perform the method and/or a program storage medium encoded with computing instructions that, when executed, perform the method.

A computer-implemented method may include obtaining seismic data acquired in a time-domain for a subterranean region of interest. The method may further include obtaining a property model for the subterranean region of interest. The method may further include determining one or more time shifts using a segment dynamic image warping function based on the seismic data and the property model. The method may further include determining an adjoint source operator using the derived time shift and one-way wave equation. The method may further include updating the property model using a gradient solver in a data-domain reflection traveltime inversion. The method may further include outputting the updated property model for the subterranean region of interest. The method may further include generating a seismic image for the subterranean region of interest using the updated property model.

A method and apparatus for identifying features of a subsurface region, including: obtaining an initial physical property model and survey data for the subsurface region; identifying a current model to be the initial physical property model; and executing one or more iterations of: generating synthetic data and forward wavefields with the current model and the survey data by forward modeling with forward wave equations representing isotropic wave-mode-independent attenuation; generating adjoint wavefields with the synthetic data and the survey data by adjoint modeling with adjoint wave equations representing isotropic wave-mode-independent attenuation; computing an objective function gradient with the forward wavefields and the adjoint wavefields by solving gradient equations with the corresponding wave equations representing isotropic wave-mode-independent attenuation; computing a search direction of the objective function; searching for a possible improved model along the search direction; and updating the current model to be the possible improved model.

Methods and devices for seismic exploration of an underground structure apply W.sup.2-based full-wave inversion to transformed synthetic and seismic data. Data transformation ensures that the synthetic and seismic data are positive definite and have the same mass using an adaptive normalization. This approach yields superior results particularly when the underground structure includes salt bodies.

There is described embodiments relating to a method of determining a wave field in an anisotropic subsurface of the Earth. The method includes numerically solving a decoupled quasi-acoustic single wave mode wave equation based on spatially varied anisotropic parameters, to determine the wave field in the anisotropic subsurface.

Techniques are disclosed relating to reducing noise in marine seismic survey data. A shot-by-shot depth migration of recorded marine seismic survey data that includes multiples wavefields indicative of surface reflections may be performed. Post-migration data generated by the migration may include angle information derived from the multiples wavefields. Attributes of the marine seismic survey data may be corrected using the angle information in order to identify a potential sub-surface structure.

Disclosed is a method and associated computer program and apparatus for characterising changes within a subsurface volume between a first time and a second time. The method comprises obtaining first seismic data corresponding to the first time and processing this data to obtain a seismic image of the subsurface volume. This processing is reversed for relevant portions of the seismic image to obtain relevant portions of first seismic data. Changes within the subsurface volume between the first time and the second time are characterised by estimating the changes between second seismic data corresponding to the second time and the relevant portions of first seismic data.

A method for processing seismic data from a subsurface using least squares migration or wave equation migration velocity analysis over a cost function comprising a function of a matching filter by iteratively updating the reflectivity model velocity model to yield an updated reflectivity model or updated velocity model that matches the observed seismic data.

A system and method is provided for restoring a 3D tomographic model of the Earth's subsurface geology from the present-day to a past restoration time. Whereas at the present time all faults represent active discontinuities, at a past restoration time some faults have not yet formed. Accordingly, the restored model divides the fault network into -active faults (discontinuous surfaces for faults that intersect the layer deposited at the past restoration time) and -inactive faults (continuous surfaces for faults that do not intersect the layer deposited at the past restoration time). A new 3D restoration transformation is also provided that uses linear geological constraints to process the restoration model in less time and generate more accurate geological images.