Abstract: A model seismic image of a subsurface seismic reflector is constructed, wherein a set of source and receiver pairs is located, and a subsurface velocity function is determined. Specular reflection points are determined on the subsurface seismic reflector for each of the source and receiver pairs. A Fresnel zone is determined on the subsurface seismic reflector for each of the specular reflection points, using the subsurface velocity function. One or more seismic wavelets are selected and a set of image points is defined containing the subsurface seismic reflector. A synthetic seismic amplitude is determined for each of the image points by summing the Fresnel zone synthetic seismic amplitude for all of the Fresnel zones that contain the image point, using the seismic wavelets. The model seismic image of the subsurface seismic reflector is constructed, using the synthetic seismic amplitudes at the image points.

Abstract: Computer-implemented methods of processing seismic data are subjected to quantitative evaluation by a computerized testing procedure. The effect of the data processing software under evaluation on attributes of the seismic data is measured and statistically evaluated. The effect of various user-selectable processing parameters of the software under evaluation is also measured and statistically evaluated. To evaluate the software effect on attributes, an attribute of known content represented by seismic data is selected. The seismic data represented by that attribute is processed by the processing software under evaluation. A test measure of the attribute is recomputed as indicated by the results of the processing. A quantitative statistical analysis of the similarities of the two attributes is then performed. For quality control of parameter estimates, a parameter-sweep test is performed on original data containing known events.

Abstract: A method of processing seismic data on parallel processors, preferably on a massively parallel processor. The input ot the process is seismic data from one or more of a number of seismic lines. The end product of the invention is a DMO corrected, zero-offset seismic image of the subsurface. By repeating the method on different input offsets, the variation in reflection strength of a reflector as a function of the angle of incidence can be examined. The method includes a two stage parallelization. First, a parallelization over the incoming traces generates a suite of DMO-corrected partial images for each point on each incoming trace. Secondly, a parallelization over output locations accumulates and combines the partial images, and produces output traces.

Abstract: Computer-implemented methods of processing seismic data for the purpose of suppression of multiple reflections, or multiples, are subjected to quantitative evaluation. The evaluation is done by a computerized testing procedure. A known earth model is formed. From this model, data composed of primary reflections only, and data containing multiple reflections only are generated. These are retained separately, but a third data set representing their sum is also formed to serve as an original data set for processing. The original data set or sum is then processed by the processing method being evaluated. The processed results are then decomposed by a time-varying, least squares technique into primaries-only and multiples-only components. The decomposed primaries-only and multiples-only components so formed are then compared against the values of the original sets from the known earth model.

Abstract: Computer-implemented methods of processing and imaging seismic data by migration and DMO (dip moveout) are subjected to quantitative evaluation. The evaluation is done by a computerized testing procedure. An impulse data set is formed containing a single "live" trace and zero amplitudes for other traces. A selected velocity function is also generated. The impulse data set is then processed by the processing method being evaluated. Estimates of the vertical traveltime, amplitude and phase along each of the impulse-response events are then generated. The estimates so formed are compared against exact values obtained from a model using an integral equation which accurately describes migration or DMO. Users thus are provided with indications of how the processing techniques may be expected to perform on real data.

Abstract: A method of geophysical prospecting wherein nonhyperbolic distortion is reduced from marine seismic data, or land seismic data over a low seismic velocity layer, is disclosed. The method comprises replacing the seismic velocity of the water or low seismic velocity layer with sediment seismic velocity and using analytic ray tracing to determine a mapping function to correct recorded seismic data for removal of the distortion, which occurs because of the high seismic velocity contrast at the water or low seismic velocity layer.

Abstract: Presented is a process for use in the area of geophysical data processing, for computing a three dimensional grid of traveltimes from a three dimensional grid of velocities. The process involves a finite-difference solution to the eikonal equation in spherical coordinates, with refinements which increase the stability of the calculation and cope with numerical roundoff error as well as turned ray problems. The resulting three dimensional grid is not only useful in itself in providing information regarding the subsurface, but also can be used in depth migration, velocity analysis (especially three dimensional tomography) and in raytracing (leading to modeling of synthetic seismograms, three dimensional traveltime inversion, and map migration). This method is preferably executed on a computer, and can be performed either on a mainframe or on a massively parallel processor.

Abstract: A method for correcting seismic data for the effects of the low-velocity-layer. According to the method, estimates of the seismic velocity in the low-velocity-layer and the depth of the low-velocity-layer are used to extrapolate the seismic data to simulated source and receiver positions located at the base of the low-velocity-layer. The data are then extrapolated to an arbitrary reference datum using a selected replacement velocity. The principles of wave equation datuming are used for these extrapolations.