Abstract: The invention pertains to the sensing and measurement of infrasound (pressure variations with frequency content under 10 Hertz). The invention measures the infrasound pressure variations and then attenuates undesired contributions due to, but not limited to, changes in ambient fluid speed and changes in altitude of the sensing device. The undesired contributions are attenuated using an adaptive filter with the measurements of the change in ambient fluid speed and the change in altitude. This approach differs from existing applications of adaptive filtering in that the invention uses measurements of speed and displacement to improve a pressure measurement. This approach differs from existing methods for attenuating the affects of the wind on the measurement of infrasound in that it does not require the use of a large spatial averaging filter.

Abstract: A method of processing seismic data comprises identifying the value of a first parameter associated with an event in a first set of seismic data. The value of a second parameter associated with a corresponding event in a second sent of seismic data is then obtained using at least one look-up table. The first parameter may be PP travel time with the first data set being a raw PP data set, and the second parameter may be PS travel time with the second data set being a raw PS data set or reflection depth. The invention makes it possible to identify pairs of corresponding PP and PS events in raw data traces. The look-up table(s) are obtained using an assumed model for the velocity of propagation of acoustic energy within the earth. The results of the method may be used in quality control, or to correct the velocity model.

Abstract: A method of predicting earthquakes includes the step of positioning a first transducer array adjacent to a seismically active region and below the water table, i.e., within the zone of saturation. The first transducer array includes a first plurality of seismometers, at least one first clock, and at least one first digitizer. The at least one first clock is in communication with at least one of the first plurality of seismometers, and the at least one first digitizer also is in communication with at least one of the first plurality of seismometers. The method also includes the steps of detecting a plurality of wave movements resulting from dilation of the crust of the Earth prior to an earthquake, and converting at least one of the wave movements into a first voltage. The method further includes the step of discriminating between wave movements resulting from dilation of the crust of the Earth and movements resulting from at least one other event.

Abstract: A method and apparatus for estimating a seismic velocity field from seismic data including time-amplitude representations associated with source-receiver locations spaced apart by an offset distance and having a midpoint therebetween, the seismic data being arranged into common midpoint (CMP) gathers associated with respective CMP locations. A control plane having an edge intersecting a plurality of the CMP locations is defined, an initial velocity field for the control plane is produced, the initial velocity field including a plurality of time-velocity values for each of the CMP locations; and an optimized velocity field for the control plane is produced by adjusting the time-velocity values for each of the CMP locations in response to trends, relative to offset distance, in time values, associated with common seismic events, until said optimized velocity field satisfies a condition.

Abstract: A method for determining a formation shear wave velocity for a subterranean formation includes propagating a multi-pole acoustic signal in a borehole using an acoustic transmitter and receiving an acoustic waveform from the multi-pole acoustic signal at one or more receivers deployed at the same circumferential position as the transmitter. The method further includes processing the acoustic waveform to determine a borehole guided wave velocity and processing the borehole guided wave velocity to determine the shear wave velocity of the subterranean formation. Isolation, suppression or enhancement of any particular harmonics of the acoustic signal is not required.

Abstract: An optical scanning system adapted to physically adjust scanner settings in response to control feature readings is disclosed. The scanner and methodology finds particular use in reading of biopolymer arrays. The system may operate in any of a number of ways such that optimal data from scans is obtained. It may also be possible to use the system as a tool to aid in manufacture of arrays by providing feedback to a manufacturer regarding the signal produce for a given batch of samples tested.

Abstract: A method intended to obtain reflection travel times from an interpretation of seismic data in migrated cylindrical waves, for a given value of the parameter defining the slope of these waves, or the superposition of such data associated with various substantially parallel acquisition lines, this parameter possibly taking successively several values. The method comprises the steps: a) defining a slowness vector ({right arrow over (p)}) b) for a given position of a seismic receiver of abscissa (XR) on an acquisition line, seeking, the abscissa (?) of the source; c) determining a travel time (te(XR)) d) repeating steps (b and c) for all the positions of the receivers for which demigration result is wanted; and e) repeating steps (a to d) for all the acquisition lines for which a demigration result is wanted and for all the values taken by parameter (px).

Abstract: A method is disclosed for processing seismic data. The method includes prestack depth migrating the seismic data to generate common image gathers using an initial velocity-depth model. Horizons in the migrated seismic data are selected. Residual migration velocity analysis in the depth-offset domain is performed with respect to each selected horizon, and the velocity-depth model is updated based on the residual migration velocity analysis.

Abstract: A method for determining a formation shear wave velocity for a subterranean formation is provided. The method includes propagating a multi-pole acoustic signal in a borehole using an acoustic transmitter and receiving an acoustic waveform from the multi-pole acoustic signal at at least one receiver. The method further includes processing the acoustic waveform to determine a borehole guided wave velocity and processing the borehole guided wave velocity to determine the shear wave velocity of the subterranean formation. Isolation, suppression or enhancement of any particular harmonics of the acoustic signal is not required.

Abstract: A number of seismic stacks are precomputed (20) for known velocity fields. The velocity fields are chosen to span the range of velocities of interest. The stacks are then arranged (21) in the 3D memory of a graphics computer (10–14) using time and position as first dimensions and the index of the velocity field as the last dimension. In such 3D space, any velocity field to be used for stacking appears as a surface (S) within a volume. Projecting the seismic stacks onto that surface provides the seismic line stacked for the velocity field of interest.

Abstract: P-wave velocity in a near-surface region of a land area is estimated from a combination of seismic data based upon waves in the near-surface region generated in response to a shock in each of a plurality of upholes drilled in the land area and vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area.

Abstract: A method for processing magnetotelluric signals to identify subterranean deposits is provided for. The methods comprise obtaining magnetotelluric data from an area of interest. The magnetotelluric data comprises the amplitude of magnetotelluric signals recorded over time at one or more defined locations in the area of interest. The data for each location then is filtered through a set of frequency filters. The frequency filters correspond to subterranean depths over a range of interest. Amplitude peaks in the filtered data then are identified and analyzed to determine a value correlated to the resistance of the earth at each frequency and location. The resistance values are indicative of the presence or absence of deposits at the corresponding subterranean depth.

Abstract: A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra.

Abstract: A method of processing seismic data, for example surface seismic data such as multi-component OBC (Ocean Bottom Cable) seismic data, comprises using vertical seismic profile (VSP) seismic data to determine a model of the relationship between depth within the earth and the velocity of seismic energy. In one embodiment, an model of the relationship between depth and velocity of seismic energy for P-waves is calibrated using VSP seismic data. Then, a model of the relationship between depth and velocity of seismic energy for S-waves is calibrated using VSP seismic data. Initially the models are calibrated for the vertical velocity of P-waves and S-waves, using zero-offset or low-offset VSP data. The models may then undergo further calibration steps, such as calibration for VTI anisotropy and anelastic attenuation. Once calibration is complete, the models are used to process surface seismic data.

Abstract: Techniques are presented for determining the drift of a clock adapted for subsurface disposal. Seismic signals are transmitted through the subsurface medium from an uphole location at selected times, acoustic signals associated with the transmitted seismic signals are received with acoustic sensors at identified downhole locations. First and second transit times for acoustic signals received at an identified downhole reference location are determined using the clock. A time difference between the first and second signal transit times at the reference point is calculated to determine the clock drift.

Abstract: A method is disclosed for the generation and application of anisotropic elastic parameters. Anisotropic elastic parameters are generated such that, for selected seismic wave and anisotropy types, an approximation to the anisotropic modeling of seismic amplitudes is obtained by the equivalent isotropic modeling with the anisotropic elastic parameters. In seismic modeling, wavelet estimation, seismic interpretation, inversion and the interpretation and analysis of inversion results anisotropy are handled with isotropic methods, when earth elastic parameters utilized in these methods are replaced by the anisotropic elastic parameters.

Abstract: A method for generating P-S or S-S seismic data from P-P AVO data in P-P travel time for a geographic area includes obtaining a plurality of amplitude and angle of incidence pairs of P-P AVO data. The plurality of amplitude and angle of incidence pairs of P-P AVO data are inverted. Lastly, estimates of the rock property contrasts are produced from the inverted plurality of amplitude and angle of incidence pairs of P-P AVO data, the rock property contrasts including at least one of ?Vp/Vp, ?Vs/Vs and ??/?.

Abstract: A method of predicting earthquakes includes the step of positioning a first transducer array adjacent to a seismically active region and at least about 3 meters below the surface of the crust of the Earth. The first transducer array includes a first plurality of seismometers, at least one first clock, and at least one first digitizer. The at least one first clock is in communication with at least one of the first plurality of seismometers, and the at least one first digitizer also is in communication with at least one of the first plurality of seismometers. The method also includes the steps of detecting a plurality of wave movements resulting from dilation of the crust of the Earth prior to an earthquake, and converting at least one of the wave movements into a first voltage. The method further includes the step of discriminating between wave movements resulting from dilation of the crust of the Earth and movements resulting from at least one other event.

Abstract: A method for determining a velocity model of seismic waves picked up by seismic receivers coupled with an underground formation, in response to the emission of seismic waves in the subsoil by a seismic source, after reflection on geologic interfaces of the formation, from multi-offset records of these waves is disclosed. From picking the seismic records of one or more events for different source-pickup pairs associated with the weakest offset of a seismic acquisition device, the geometry of the events is predicted for the total range of offsets of the acquisition device and for different velocity values taken around a reference layer velocity, by means of kinematic inversion and modelling techniques. Then, for different lateral positions of the acquisition device, the predicted travel time curve best approaching the seismic event considered is selected. The travel times thus obtained are then supplied to a prestack inversion method such as a travel time tomography.

Abstract: Method of removing irregularities caused by tube waves from seismic data obtained in a borehole seismic survey, using a set of seismic or sources and a set of seismic receivers each arranged in a borehole, in which seismic data is time shifted based on an estimated tube wave velocity, filtered and then the time shift is reversed and applied to the original data set resulting in a corrected set, which is again time shifted opposite to the original time shift to remove and identify tube wave irregularities.

Abstract: A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra.

Abstract: A method and apparatus for imaging subsurface fractures using an ST plane for quick looks and quality checks at the wellsite. Incident angles of impinging acoustic waves with respect to receivers are estimated from actual and apparent slowness, and the position of the fracture is estimated from the travel time and incident angle. The fracture can be imaged by plotting values from the ST plane onto the position of the fracture.

Abstract: Optical detection techniques for the assessment of the physiological state, health and/or viability of biological materials are provided. Biological materials which may be examined using such techniques include cells, tissues, organs and subcellular components. The inventive techniques may be employed in high throughput screening of potential diagnostic and/or therapeutic agents.

Abstract: A method for determining a velocity model of seismic waves picked up by seismic receivers coupled with an underground formation, in response to the emission of seismic waves in the subsoil by a seismic source, after reflection on geologic interfaces of the formation, from multi-offset records of these waves is disclosed. From picking the seismic records of one or more events for different source-pickup pairs associated with the weakest offset of a seismic acquisition device, the geometry of the events is predicted for the total range of offsets of the acquisition device and for different velocity values taken around a reference layer velocity, by means of kinematic inversion and modelling techniques. Then, for different lateral positions of the acquisition device, the predicted travel time curve best approaching the seismic event considered is selected. The travel times thus obtained are then supplied to a prestack inversion method such as a travel time tomography.

Abstract: The present invention provides a method for reducing water bottom reflection time differences. The method includes selecting a plurality of trace groups, each trace having an offset from a midpoint and a water bottom reflection time. The method also includes determining a rate of change of the water bottom reflection time of each trace and generating a model water velocity and a model water bottom reflection time for each trace midpoint using a preselected function of the water bottom reflection times and the rates of change. Furthermore, the method includes generating a plurality of water bottom reflection time corrections for the traces in each trace group using a pre-selected function of the water bottom reflection times, the model water bottom reflection times, the model water velocities, and the trace offsets.

Abstract: The present invention provides for a method of processing mode converted seismic data. The method comprises acquiring seismic data and determining a P-wave velocity model for the seismic data. An S-wave velocity model is determined from the P-wave velocity model. The mode converted seismic data are depth migrated forming CIP mode converted seismic data gathers. Corrected S-wave velocities are determined from near-offset data of the CIP gathers which corrects the depth migrated mode converted seismic data to the P-wave velocity model depth. A correction factor is provided and the iterating with the method quickly converges to a solution. This invention provides an efficient method of updating the shear wave velocity model for prestack depth migration of mode-converted data.

Abstract: A method is provided for ensuring increased accuracy and stability in analysis of seismic trace data. The present method more accurately determines the location, as well as the saturation level, of possible hydrocarbon reservoirs. The method includes use of more accurate, non-linear equations for the AVO inversion and application of a geologically reasonable set of statistical constraints.

Abstract: A method is disclosed for examining a body by transmitting the N continuous orthogonal signals, generated in accordance with the disclosed method, into the body and providing receivers for receiving and recording the N signals including reflections of the N continuous signals from one or more reflectors within the body. The travel-time to the reflectors for each of the N signals at each of the receivers is determined by cross correlating each of the N signals with each of the recorded signals at the receivers.

Abstract: The patent discloses a signal processing technique for determining the fast and slow shear wave polarizations, and their orientation, for acoustic waves in an anisotropic earth formation. The signal processing method decomposes composite received waveforms a number of times using a number of different strike angles. The decomposed signals are used to create estimated source signals. The estimated source signals are compared in some way to obtain an objective function. Locations in a plot where the objective function reaches minimum values are indicative of the acoustic velocity of the fast and slow polarizations within the formation.

Abstract: Providing a set of seismic sources in a focusing array to enable concentrating seismic energy in a selected target point (k) in an underground formation, by performing a standard seismic survey of the underground formation using a set of impulsive seismic sources and a set of downhole seismic receivers j, and recording the signals uij(t), selecting a position k to be the target point; obtaining from the signals uij(t) the one-way travel times &tgr;ik from a number of sources i to the target point at the location k; and calculating ti=t0−&tgr;ik to obtain the activating times ti at which the impulsive seismic sources i have to be activated, in order to get a focusing array of the seismic sources i of which the seismic waves arrive at the target point k in phase at time t0.

Abstract: A method for generating P-S or S—S seismic data from P—P AVO data in P—P travel time for a geographic area includes obtaining a plurality of amplitude and angle of incidence pairs of P—P AVO data. The plurality of amplitude and angle of incidence pairs of P—P AVO data are inverted. Lastly, estimates of the rock property contrasts are produced from the inverted plurality of amplitude and angle of incidence pairs of P—P AVO data, the rock property contrasts including at least one of &Dgr;Vp/Vp, &Dgr;Vs/Vs and &Dgr;&rgr;/&rgr;.

Abstract: The present invention provides a method of determining source and receiver static corrections for seismic data that does not depend on user supplied velocity parameters or input models. The method comprises decomposing first break seismic data arrivals into source id terms, receiver id terms, offset terms and average datum correction terms. The source id terms and receiver id terms and offset terms are applied to the seismic data to obtain residual first break times. Average datum correction terms are determined by forming a nonlinear equation for a least-squares fit of the residual first break times as a function of elevation difference. At least one receiver static correction term is determined from the receiver id terms and receiver average datum correction terms. At least one source static correction is determined from said source id terms and source average datum correction terms.

Abstract: A seismic prospection method in which a compression seismic wave is emitted into the subsoil and sensors are used to collect seismic data having at least a shear component, and in which the data corresponding to said shear component is processed to deduce information about the geology of the subsoil, the method being characterized in that an estimate of the ratio: ∫ Z 0 Z ⁢ v p ·   ⁢ ⅆ l / ∫ Z 0 Z ⁢ v s ·   ⁢ ⅆ l is determined where vp and vs are values for real loca

Abstract: A method for determining formation shear slowness of formations surrounding an earth borehole that includes: transmitting sonic energy into the formations from a dipole source in the borehole; measuring signals from orthogonal wave components that have traveled through the formations at each of a plurality of receiver locations in the borehole, spaced at a respective plurality of distances from the transmitter location; transforming the signals to the frequency domain and separating dispersive and non-dispersive portions of the transformed signals; and determining fast and slow shear slowness of the formation from the low frequency asymptotes of the dispersive portions of the transformed signals. Related methods for determining shear directionality and the magnitude of anisotropy of anisotropic formations surrounding an earth borehole and associated apparatus are also described.

Abstract: A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra.

Abstract: A method for determining properties of a transverse isotropic region of earth formations traversed by a wellbore having substantially vertical and deviated sections therethrough, including measuring sonic velocity properties in formations surrounding the substantially vertical section of the wellbore; measuring sonic velocity properties in formations surrounding the deviated section of the wellbore; and determining, from the measured velocities, all of the transverse isotropic elastic constants of the region.

Abstract: A signal can be analysed to determine statistical characteristics indicative of, for example, the predictability or time reversibility of the signal. The signal is examined to locate events corresponding to the crossing of predetermined levels with predetermined slopes. Multiple versions of the signal are combined, the versions being shifted with respect to each other by amounts corresponding to the spacings of the detected events. The shape of the resulting representation provides statistical information regarding the signal.

Abstract: The present invention comprises methods and a computer-readable medium comprising programming code for automatic statistical modeling of data. In an embodiment, the analysis is completely automatic with a single computer stroke providing an analysis of data with at least nineteen independent variables. The output is provided in multiple formats, as for example, graphs, reports, spreadsheet files, and an electronic calculator. In an embodiment, approximations of missing data can be automatically calculated and used in the model. The modeling systems and software of the present invention may be used to provide information necessary for manufacturing, business models, scientific endeavors, transportation schedules, and other practical applications.

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: A seismic velocity analysis method includes tying velocity parameter values such as residual velocity values to geological horizons (reflectors) within a seismic exploration volume. Common image gathers (CIGs) such a common reflection point (CRP) gathers or angle-domain common image gathers (ACIGs) are generated for a set of CIG grid points. Computed best-fit residual velocity values are then snapped to a neighboring horizon or vertically interpolated to the horizon, to generate residual velocity values along the horizon. The residual velocity values for points along the horizon are then selectively employed in updating the velocity model for the volume of interest.

Abstract: A method of seismic analysis is disclosed for determining geopressures or seismic velocities or other formation attributes. In one embodiment, a frequency related attribute is determined from seismic data by analysis of the frequency content of one or more signal traces. Geopressure or velocity may then be derived from the frequency related attribute without reliance on moveout techniques. In another embodiment, a derivative of a maximum value of pore pressure is utilized to determine a transition zone whereby the derivative peaks and then recedes. The lithology is then examined to determine a formation directly below the transition zone at which an overpressure may exist.

Abstract: A method is disclosed for controlling the quality of seismic data acquisition. The method includes generating a scattered acoustic wavefield and receiving at least a portion of the scattered wavefield. At least a portion of the received wavefield is substantially deghosting relatively near the acquisition site. The deghosting includes transforming the received scattered acoustic wavefield into the spatial frequency domain with respect to the in-line and cross-line directions, separating a ghost wavefield from the received wavefield and transforming the separated wavefield into the space-time domain. The quality of the substantially deghosted scattered acoustic wavefield below the surface of the water scattered acoustic wavefield is then evaluated.

Abstract: A method for determination of seismic wave travel times from a surface location to at least one subsurface computation point (CP) within a plurality of subsurface location points. A velocity model of a region is defined. A complex monochromatic wavefield is computed, using the velocity model, for the at least one CP. An unwrapped phase of the seismic wave is determined at a neighboring computation point (NCP) proximate to at least one subsurface CP. The travel time of the seismic wave to the at least one CP is determined using the unwrapped NCP phase and the computed monochromatic wavefield for the at least one CP. Travel time maps and table may be created from the determined travel time values.

Abstract: The invention concerns a method for detecting geological discontinuity in an environment using an optical flow. The method includes the steps of selecting in the seismic block a section containing at least one discontinuity. The section constitutes a seismic image. The method includes computing a rough optical flow on the seismic image to obtain a first representation of an optical flow wherein the discontinuity constitutes a moving front. The method also includes smoothing, by a non-supervised dynamic cluster process, the optical flow representation so as to obtain a second optical flow representation wherein the discontinuity shows accentuated contrasts.

Abstract: A method is disclosed for determining compressional (P) wave and shear (S) wave velocities from seismic data acquired using multiple component receivers. The method includes estimating interval velocity of P waves from earth's surface to a first reflector from P wave arrivals in the seismic data. A interval ratio of P wave to S wave velocity is estimated from earth's surface to the first reflector from P-S wave arrivals in the seismic data. An S wave interval velocity is estimated from the estimated P wave interval velocity and interval ratio. A depth is determined from the earth's surface to the first reflector using each of the P wave and S wave estimated interval velocities, the depths to the first reflector estimated using each of the P wave and S wave estimated interval velocities are balanced.

Abstract: This invention relates to a method for determining direction and relative magnitude of maximum horizontal stress in sedimentary basins within Earth's crust. In particular the method uses seismic reflection data in determining the direction and magnitude of stresses. The method involves identifying from seismic data faults which cut the upper continental crust and uses those faults in conjunction with globally simultaneous compressional structures such as anticline to map the horizontal stresses. The invention has a particular application in the hydrocarbon exploration and production industry and has the advantage of providing the results pre-drill.

Abstract: A method and apparatus for reliable and low-cost acquisition of offset checkshot survey data using tube wave conversion. An acoustic receiver is deployed in a fluid-filled well, preferably at or near the top thereof. At least one tube-wave conversion point is used, such as an interface between two immiscible fluids, a change in casing geometry or a wellbore constriction. The traveltime of a tube wave from the tube-wave conversion point to the acoustic receiver is determined. Then, a seismic signal is generated at a laterally offset location. The total seismic signal traveltime along a raypath from the source location to the tube-wave conversion point and then upwardly through the fluid-filled well to the acoustic receiver is measured. The previously determined tube-wave traveltime from the conversion point to the acoustic receiver is then subtracted from the total traveltime to obtain the seismic signal traveltime from the source location to the tube-wave conversion point.

Abstract: A prestack migration method allowing imaging of an underground zone, for a given velocity model of arbitrary complexity. The method allows obtaining elementary migrated images associated with the values assumed by a parameter and the sum of the images obtained for the different values of the parameter (post-migration stacking), in the depth domain as well as in the time domain. This migration is independent of the volume of the results calculated and of the number of seismic traces recorded. Volume images are obtained by taking account of all the seismic traces. Azimuth movout correction is applied to the received data to compensate for drift.

Abstract: Recursive f-k migration of a body of seismic data performed in N stages, including establishing from an RMS velocity VRMS a laterally-averaged interval velocity profile extending from a surface at time zero to time t; determining layer boundaries within the laterally averaged interval velocity profile, including identifying a unique set of pairs of depth and vertical travel time giving rise to a minimum sum of squares of residuals for the layers; calculating reference velocities for each layer; time-stretching the entire body of seismic data; performing, upon the data in each layer of the body of seismic data not yet fully migrated, recursive stages of f-k migration, including using as input to a current recursive migration stage that portion of the output from a previous recursive migration stage that comprises data partially migrated; and inversely time-stretching the entire body of seismic data.

Abstract: This invention removes the effects of variable water velocity by calculating and applying corrections that map the seismic data to an ideal case of constant water velocity. All of the corrections assume, from a separate analysis step, that the vertical (zero-offset) timing errors induced by the water-velocity variations and that the zero-offset water bottom times are available. Equivalently, the water velocities are assumed known. The timing errors and water velocities are related. The zero-offset water-bottom times are also assumed available. From this information, and an arbitrarily-defined “ideal” water velocity, it is possible to calculate an observed (actual) water velocity relative to the “ideal” case. The only additional information needed is the angle of the ray path through the water layer. The angle may be calculated directly from normal moveout velocities derived from conventional analysis of the seismic data, and the information above.