Abstract: An acoustic classification system in which echoes from sediment-sediment or water-sediment interfaces are compared to model waveforms predicted by Biot's equations for a given set of acoustic material parameters. The selection of parameters are varied until a match occurs, indicating the correct parameters of the reflecting sediments. Preferably, the variation of selected test parameters is conducted by formal search algorithms, such as simulated annealing or genetic algorithms, to increase computational efficiency.

Abstract: The two-way water-layer travel time, .tau., is derived from duel-mode seismic sensor data by cross-correlating the Fourier transforms of the sum and difference of the velocity and pressure signatures. The Z-transform of .tau. evaluates one of the two Backus variables, Z.sub.w. The second variable is R.sub.b, the water bottom reflectivity coefficient. The frequency-domain transforms of the above summed and differenced signatures are each multiplied by the Backus operator (1+R.sub.b Z.sub.w).sup.2 after initializing R.sub.b and the products are iteratively cross-correlated until the correlation function converges to a minimum. R.sub.b is perturbed after each iteration. The value of R.sub.b upon convergence is the local water bottom reflectivity coefficient.

Abstract: A method for making a 3-D cube of near traces from data acquired in a marine reflection seismic survey.A method for making a 3-D cube of near traces using at least one source (S.sub.1, S.sub.2) and a plurality of streamers (4 to 7) spaced from the source, each comprising receivers/recorders (R.sup.1.sub.4, R.sup.1.sub.5, R.sup.1.sub.6, R.sup.1.sub.7) as well as means for the space tracking of each source and each streamer, the image of the subsurface being produced in three dimensions with a system of X, Y, T axes in the form of a 3-D cube by assigning to each bin of a group of bins forming a group with a regular grid in an X,Y plane, a central trace represented at the center of said bin along the time axis (T), said method being characterized in that for each line navigated, said central trace is produced from at least a first recorded trace whose offset is as close as possible to a constant offset equal to the smallest offset common to at least the group of traces of the navigated line.

Abstract: A method and computer system for applying corrections to dual sensor ocean bottom cable marine seismic signals, for purposes of eliminating ghosts and reverberations, are disclosed. According to the disclosed method and system, both phase and amplitude corrections are derived in common receiver gathers, and applied to each geophone trace in the gather; preferably, the derivation of the corrections is performed on a limited offset common receiver gather. The phase correction is determined by minimizing a folded cross-correlation of the hydrophone and geophone signals over varying phase angles, with the appropriate phase correction corresponding to the angle at which the minimum is obtained; preferably, stacked cross-correlations are used in the phase correction determination to reduce the effects of random noise. The phase correction is then applied to the geophone traces in the gather, and an amplitude correction is derived by minimizing a cross-ghosting relationship.

Abstract: A method for eliminating the influence of multiple reflections in seismic data by determining an up going and down going vector wave-field from the vector wave-field, determining a product of the free surface reflection coefficient and the down going vector wavefield, and adding the product to the up going vector wave-field. Also provided is a method for eliminating the effects of receiver coupling from seismic data taken in a survey by describing a first cross-equalization filter as a function of the reverberation period, describing a second cross-equalization filter as a function of the seismic data, describing an inverse coupling filter as a function of the first cross-equalization filter and the second-equalization filter, and applying the coupling filter to the seismic data.

Abstract: A computationally economical method for applying multi-dimensional multiple-reflection attenuation to a marine seismic-signal data set comprised of a plurality of common shot gathers that have surface-multiple wavefields embedded therein. The multi-dimensional data are assumed to have been gathered from a plurality of parallel 2-D lines of survey. From every nth reference line, where n is a small number greater than 2, a common shot gather is selected. For every so-selected common shot gather, a reference surface-multiple wavefield is predicted as a function of offset and travel time with the aid of any well-known multiple attenuation routine, using a wavelet having fixed attributes in terms of amplitude, phase and frequency. A common shot gather is chosen from among the plurality of common shot gathers.

Abstract: A receiver consistent deconvolution operator models the damped oscillatory wavetrain that is related to geophone coupling to the water bottom. The operator is a best-fitting function that endeavors to describe the difference in coupling response between a well-coupled in-line geophone relative to an imperfectly-coupled cross-line geophone. The operator is applied to the cross-line signals to compensate the signals for the distortion due to imperfect cross-line ground coupling.

Abstract: A marine seismic surveying method recording with a first sensor a first signal indicative of pressure and with a second sensor a second signal indicative of motion, calculating a coupling mechanism filter for the second signal substantially correcting for the imperfect coupling of the second sensor, and applying a filter based on the coupling mechanism filter to at least one of the signals.

Abstract: A method for minimizing non-uniform insonification of subsurface formations in the presence of steep dips when advancing a swath of elongated parallel seismic streamer cables along a line of survey. A first acoustic source is stationed at the leading end of the swath and a second source is stationed at the trailing end of the swath. The sources are activated in alternate cycles at preselected timed intervals to provide down-dip and up-dip seismic data sets. The data sets are processed and merged to eliminate objectionable shadow zones.

Abstract: A signal processing system provides and processes a digital signal, generd in response to an analog signal, which includes a noise component and possibly also an information component representing three mutually orthogonal items of measurement information representable as a sample point in a symbolic Cartesian three-dimensional spatial reference system. A noise likelihood determination sub-system receives the digital signal and generates a random noise assessment of whether or not the digital signal comprises solely random noise, and if not, generates an assessment of degree-of-randomness. The noise likelihood determination system controls the operation of an information processing sub-system for extracting the information component in response to the random noise assessment or a combination of the random noise assessment and the degree-of-randomness assessment.

Abstract: A computer-implemented method and system of correcting seismic survey data for the effects of NMO stretch is disclosed. The method operates upon a CDP gather of seismic survey data after normal move-out correction (NMO) has been applied. A semblance analysis is used to derive a stretch coefficient .kappa. profile over the gather, as a function of time and offset. The values of the stretch coefficient profile .kappa. are used in producing a time-varying filter that is applied, preferably by way of a time-domain multiplication, to incremental windows in time for each trace, with the products added to one another to generate a corrected trace. After all of the traces in the gather are corrected, an event-weighted filter is applied to the traces by way of a correlation operation, to remove high-frequency artifacts in the corrected traces. The corrected and filtered traces are then ready for stacking and conventional processing.

Abstract: A method and apparatus for analyzing amplitude-versus-offset (AVO) seismic data to distinguish sand formations, such as Morrow sands, from limestones and other similar intervals, is disclosed. For each of the traces in the survey, AVO intercept and AVO slope traces are generated, preferably after normalization of the amplitudes of the traces to account for geophone coupling variations. After normalization and conventional processing and corrections, spatial summation may be performed to further improve the traces. AVO trend lines are then generated, preferably on a weighted window basis, to generate localized trend lines against which the intercept and slope values of individual depth points may be compared. This comparison allows the plotting of AVO intercept versus AVO slope deviation from the trend line, from which sand formation interfaces may be identified by their presence in certain quadrants of the intercept-slope deviation cross-plot.

Abstract: A system for acquiring and processing seismic data comprises source-means for generating sound waves and receiver-means for recording as data those waves as reflected from sub-surface interfaces, and means for processing the recorded data operable to generate sets of actual data each individually associated with specific sub-surface reflection points, order the data-sets in accordance with receiver and source-means separation, process each data-set to generate additional data intermediate the recorded data, and re-order each data-set and additional data in accordance with receiver and source-means separation for further processing. Each data-set is applied to a filter to generate said additional data intermediate of the recorded actual data. The filter is selected from the group comprising linear, quadratic or spline interpolation filters, frequency space (f-x) filters, tau-p filters, smart filters artificially intelligent filters, neural network filters and (preferably) sinc filters.

Abstract: A method for efficiently and accurately migrating seismic data recorded from an area of interest is disclosed. The method utilizes determining displacement values for every output sample in an area of interest, preferably by generating a displacement section from a velocity section and depth model. The displacement values are then used to select a migration aperture for the migration algorithm.

Abstract: Disclosed is a programmable data collection and relay circuit for a towed hydrophone array. The circuit is designed to prepare data concerning operation of the array to be interleaved with substantive data produced by the hydrophones to produce a single data stream for transmission to recording equipment. The circuit comprises (1) a plurality of sensor inputs, each of the sensor inputs adapted to be coupled to a sensor capable of sensing a physical characteristic within the towed hydrophone array, (2) a circuit for polling at least a portion of the plurality of sensor inputs to determine values of the inputs, (3) a circuit for storing programmed data concerning which of the plurality of inputs is to be polled and (4) a circuit for serially placing the input values in condition for insertion into a data stream transmitted along the towed hydrophone array.

Abstract: A marine seismic signal is transformed from time domain into frequency domain and represented by matrix D. The marine data signal is truncated in time, transformed into the frequency domain and represented by matrix D.sub.T. Eigenvalue decomposition D.sub.T =S.multidot..LAMBDA..multidot.S.sup.-1 of matrix D.sub.T is computed. Matrix product D.multidot.S is computed and saved in memory. Matrix inverse S.sup.-1 is computed and saved in memory. An initial estimate of the source wavelet w is made. Source wavelet w is computed by iterating the steps of computing diagonal matrix [I-w.sup.-1 .LAMBDA.], computing matrix inverse [I-w.sup.-1 .LAMBDA.].sup.-1, retrieving matrix product D.multidot.S and matrix inverse S.sup.-1 from memory, and minimizing the total energy in matrix product [D.multidot.S] [I-w.sup.-1 .LAMBDA.].sup.-1 S.sup.-1. Primary matrix P representing the wavefield free of surface multiples is computed by inserting computed value for w into the expression [D.multidot.S] [I-w.sup.-1 .LAMBDA.].sup.-1 S.

Abstract: A method for improving seismic sections includes generating seismic signals at source stations, recording seismic traces at receiver stations and gathering the seismic traces as a first gather at a common point as a function of the offsets between the source stations and the receiver stations. A common point (MMOCMP) is selected, a half-offset between source and receiver stations is redefined as a function of the distance between the selected common point MMOCMP and the RAWCMP, and the seismic traces are sorted as a function of the redefined half-offset, constituting a second gather of traces. The method permits one to obtain true located subsurface information at any desired point for velocity analysis.

Abstract: Disclosed is a telemetry data transmission circuit for a towed hydrophone streamer, the streamer comprised of a plurality of series-coupled modules. The transmission circuit comprises: (1) a slave clock input in a first module capable of receiving a master timing signal from a master clock source located in a second module, the master timing signal capable of synchronizing an operation of the transmission circuit to allow the transmission circuit to place local telemetry data on a data bus coupled to the transmission circuit and running a length of the streamer, (2) a local clock input in the first module capable of receiving a local timing signal from a local clock source located in the first module, the local timing signal alternatively capable of synchronizing the operation of the transmission circuit and (3) a clock source selection circuit capable of allowing the local clock source to synchronize the operation of the transmission circuit as a function of a condition of the master timing signal.

Abstract: A method for measuring the velocity of shear waves in a formation beneath a body of water. The shear wave velocity is derived from the parameters of water density, water-bottom reflection coefficient, formation compressional wave, velocity and the propagation velocity of a submarine ground-roll wave front.

Abstract: A method of reducing effects of noise in seismic signals generated by a plurality of seismic sensors at spaced apart locations from a seismic source is disclosed. Each of the signals is represented by a signal trace in a record section. The method includes the steps of isolating noise in the signal traces, time aligning corresponding portions of the noise in the traces thereby generating time-aligned noise traces, stacking the time-aligned noise trace to generate a stacked noise trace, replicating the stacked noise trace at each corresponding trace position in the record section, restoring the replicated traces to the original trace time positions by reversing the step of time-aligning to generate noise signature traces, comparing the noise signature traces to corresponding signal traces to generate filters which substantially minimize a measure of the difference between the noise signature traces and the signal traces.

Abstract: A meso-scale profiling tool has separate upward and downward focused seismic sources, separate upward looking and downward looking directional receivers and a section of the tool containing the sources and receivers adapted to rotate with respect to the remainder of the tool so that the sources and receivers are always in a proper substantially vertical orientation.

Abstract: A computer driven system which receives time-binned echo strength data, and hich, for each series of echo strengths received, stores the echo strength data in computer memory, and automatically associates with that data the latitude, longitude and time at which the data were generated. From these data, the algorithm classifies the sediments, which produced the echo strengths, determining such parameters as sediment acoustic impedance, porosity, attenuation, grain size, density, acoustic velocity, and shear strength. System software can produce additional result files in which these properties are associated with corresponding echo strength data. Both the raw and reduced data are displayable in human readable form, preferably on a computer monitor, for operator review. System software can also generate navigation plots which trace on a map, preferably on computer monitor, points at which data are taken, and the bottom sediment at those points.

Abstract: A method for improving the signal to noise ratio from a pair of detectors such as geophones which each detect a noisy signal comprising a signal of interest (S) and a noise signal (N), wherein the signal of interest (S) has a different moveout across the pair of detectors from that of the noise signal (N), and the noise signal (N) from a given source is detected at the first detector at a time .DELTA.t before the corresponding noise signal is detected at the second detector, the method comprising delaying the noisy signal (S+N) detected at the first detector by an amount .tau. being greater than the moveout of the signal of interest but not more than .DELTA.t and subtracting the delayed signal from that detected at the second detector by means of an adaptive filter so as to minimize the power in the resultant signal. The signal detected at the first detection and optionally the resultant signal can also be delayed by an amount .tau..sub.

Abstract: The system includes a plurality of acquisition devices (A.sub.i) for collecting signals received by receivers (Rk) and a central control, recording and processing station. This station manages the performance of the devices (A.sub.i), of successive signal acquisition cycles and thereafter the centralization thereof. In order to relieve the central station of part of the tasks thereof in case of a high volume of data to be collected and processed, acquisition devices are used which have management processors (2, M.sub.1, M.sub.2) and with complementary computing processors (7, M.sub.3) programmed for carrying out processings of the data before the transmission thereof. Various combinations of seismic signals, data compression, and quality controls are performed in real time during the phase of setting of the seismic equipment (seismic receivers and acquisition device electronics (CA1 to CAn) in the devices A.sub.i in the field), etc, immediately accessible to operators in the field.

Abstract: Pressure and velocity seismic signals are combined, the combined signal is transformed into the frequency domain and multiplied by the inverse Backus operator or the combined signal is convolved with the inverse Backus operator, and an optimization algorithm is utilized to solve for water bottom reflectivity. Pressure and velocity seismic signals are combined, and the combined signal is multiplied by the inverse Backus operator containing the water bottom reflectivity to eliminate first order peg leg multiples.

Abstract: A process for the extraction of a time-variable useful signal having a finite spatial extension by an array of N sensors or transducers (N being equal to or greater than 3), that receive the useful signal to which have been added q spatially coherent additive noises (q being less than N). According to the process, unprocessed signals are acquired on the output of each sensor, filtered in order to restrict them to the frequency band of the useful signal and digitized. Then, spatial prediction error signals of the noise are calculated and analyzed so as to carry out the detection of the useful signal and its separation from the q additive noises. A device for extracting a useful signal according to the process is also disclosed.

Abstract: Disclosed is a protocol for transmitting data in a towed hydrophone streamer, including a transmission method and a data frame. The method comprises the steps of (1) receiving a portion of the data frame into a data transmission circuit within a particular module of the streamer, the portion of the data frame representing telemetry data derived from an adjacent module, the transmission circuit transmitting the portion of the data frame to a desired destination, (2) receiving an end-of-data signal into the transmission circuit, the end-of-data signal commanding the transmission circuit to add telemetry data derived from the particular module to the portion of the data frame and (3) adding the data derived from the particular module to the portion of the data frame, the data frame thereby transmitted to the destination and including the data derived from the particular module, the telemetry data ordered within the frame as a function of an order of modules within the streamer.

Abstract: A method for adaptively creating a filter for removing coherent environmental noise from a multitrace digitized seismic recording requires the presence, on the recording, of a limited sample of pure noise that is uncontaminated by desired signal. The pure noise sample is used to discover the location of the noise source and from that discovery, to extrapolate and reconstruct the characteristics of the noise envelope as it would appear on the seismic recording. The reconstructed noise envelope is used as a noise reference for input to a conventional iterative adaptive noise cancellation filter loop. For stability, the loop gain is minimized by temporally and spatially averaging the filter coefficients for each sample interval.

Abstract: Seismic data from co-located sensors of different genera are formatted into common velocity-receiver gathers and common pressure receiver gathers. A first ratio between the velocity signature amplitudes and the pressure signature amplitudes is measured within a fixed analysis window. A second ratio is measured between the pressure and velocity signatures for a weighting-zone window of limited extent. The first and second ratios are combined to form an equalization operator. The pressure and velocity signatures from within the weighting zone window are combined in the presence of the equalization operator to define a transient-free time-scale datum.

Abstract: A method for displaying seismic data to provide direct indications of the presence of hydrocarbons. Seismic data is processed using conventional amplitude versus offset techniques to obtain zero offset reflectivity, or A, traces and the amplitude versus offset slope, or B, traces. AB cross plots of each trace are then generated. Each sample point on the cross plot is then assigned a value corresponding to its deviation from the regression line of the cross plotted AB points. The assigned values are then plotted in their corresponding time sample positions to generate a trace or display providing a direct indication of hydrocarbons.

Abstract: An off-shore seismic prospecting method for enabling at least two ships to prospect over a single site simultaneously, in which each of the ships generates disturbances in the off-shore environment and uses sensors to record seismic traces containing useful information concerning the geology of the subsoil. A ship is liable to constitute a point source of noise for another ship, which noise gives rise to an undesirable signal that masks said useful information. According to the invention said point source of noise is localized in three dimensions and the space-time coordinates thereof [(X'(t), Y'(t), Z(t)] during the recording is stored in terms of a frame of reference in which the space-time coordinates [(X.sub.r (t), Y.sub.r (t), Z.sub.r (t)] of the sensors are also recorded, after which the recorded seismic traces are processed as a function of the space-time coordinates of the point source of noise in order to eliminate said undesirable signal.

Abstract: The invention is a method and apparatus for conducting seismic analysis of underground formations that offers improved accuracy in locating strata that contain natural gas in paying quantities. The method analyzes the resonant response generated when a seismic wave passes through a given stratum. Seismic data are collected using conventional field acquisition methods. Following conventional preprocessing, the seismic response data are mapped onto the quefrency domain in order to separate the resonant and non-resonant components of the reflected energy. Strata that consist of predominantly elastic materials (solids and liquids) resonate in discrete frequency bands, which are represented by a quefrency spectrum with a large amplitude at high-quefrency values. Gas-bearing strata have more plastic properties, and emit a more uniform response that lacks distinct resonant peaks. The quefrency spectrum of gas-bearing strata contains a relatively higher amplitude at low-quefrency values.

Abstract: A method for obtaining seismic data in frigid regions without interference from flexural ice waves. In an exemplary embodiment, seismic data is produced by using an energy source to generate a seismic wave in a floating ice sheet. Seismic disturbances caused by the energy source are detected by one or more hydrophones and geophones, which produce hydrophone and geophone response signals, respectively. In a first embodiment, the hydrophone response signal is integrated. The integrated signal and/or the geophone response signal are scaled, and the two signals are then added. Alternatively, instead of integrating the hydrophone response signal, the geophone response signal may be differentiated prior to scaling and summing. A method is also disclosed for overcoming phase errors that might be introduced, for example, by the use of a transformer-coupled hydrophone.

Abstract: A method for determining water bottom reflectivity in dual sensor seismic surveys is disclosed. The method eliminates the need for a separate survey to collect calibration data. The method involves summing the pressure and velocity signals, and multiplying the result by the inverse Backus operator, and then solving for the ocean bottom reflectivity R utilizing an optimization algorithm.Also disclosed is a method for combining the dual sensor data which results in the complete elimination of the first order peg-leg multiples and the modulation of the sub-surface reflector strength with the ocean bottom reflectivity. The method involves summing the pressure and velocity signals, and multiplying the result by the inverse Backus operator containing the correct value for the ocean bottom reflectivity R found with the method described above.

Abstract: A monitoring device for portable breathing apparatuses having a manometer by means of which the pressure in the pressure container of the breathing apparatus is detected, and having a transmitter by means of which a signal corresponding to the pressure is transmitted at regular intervals. The transmitter also has a signal generating device which generates an identification signal which is characteristic of the transmitter. The pressure signal and identification signal are received and tested by a receiver. If the identification signal matches an identification comparison signal stored in the receiving device, the measured pressure value is displayed on a display device.

Abstract: A method for reducing the effects of reverberation on noisy seismic wavefields recorded from within a moisture-laden environment. The wavefield manifests itself as a pressure signature and a velocity signature that contains an embedded nose signature. The pressure signature is adaptively filtered and subtractively combined with the velocity signature to isolate a nearly pure noise signature. The nearly pure noise signature is added back to the original velocity signature with opposite sign to clear away the embedded noise, leaving a refined velocity signature. The refined velocity signature iteratively is scaled and summed with the pressure signature, incrementing the scale factor at each iteration and autocorrelating the sum. A coefficient of convergence is calculated after each summation. The coefficient of convergence that most closely approaches unity identifies the preferred scale factor.

Abstract: A method for reconnection and connection of sensor groups, especially hydrophone groups or channels in a seismic cable, where the active sections in the seismic cable are connected with electronic modules or one another via connector plugs, is based on the principle that a specific number of hydrophone groups are connected symmetrically on each side of each electronic module. The number of connected hydrophone groups on each side is identical and constitutes at least one respective active section. A summation of a set of hydrophone groups in a section is performed automatically by connecting this section with another section or by connecting a respective section and the electronic module.

Abstract: The method sequentially determines dips and corresponding estimated dip components of traces in a panel of data. The method can be applied to any data which can be represented as a function of two coordinates. In particular, the method can be applied to seismic data traces. The method in one embodiment sums data on traces along a preselected range of trial dips on a panel of data. The energy of the summed data with their corresponding trial dip are then displayed. The dip which has the peak of maximum energy on the display is then selected as a valid dip. An estimated dip component of the selected dip is then determined and subtracted from the traces along the selected dip. The process is then repeated, sequentially, determining a dip and an estimated dip component from the panel of data until the desired number of dips and estimated dip components are determined or the residual energy of the remaining data on the traces are below a preselected value.

Abstract: A set of raw common shot gathers are resorted as common receiver gathers. The wavefield envelopes from the common receiver gathers are migrated using one half the near-surface velocity to provide migrated data sets. The migrated data sets are resorted back into common shot gathers and subtracted from the original raw common shot gathers to provide coherent-noise-reduced data sets.

Abstract: A method and apparatus for attenuating bulge wave noise from data recorded by seismic streamers is provided. The apparatus includes a marine seismic streamer having a seismic detector and an accelerometer. The accelerometer is secured between the lead-in section and the seismic detector. Intra-shot and inter-shot accelerometer and seismic detector signals are recorded. The method utilizes inter-shot and an intra-shot adaptive processing loops. The inter-shot adaptive processing loop derives inter-shot complex weights from inter-shot accelerometer signals and inter-shot seismic detector signals. The intra-shot adaptive processing loop models bulge wave noise in the intra-shot seismic detector signals by combining the inter-shot complex weights with intra-shot accelerometer signals. Bulge wave noise attenuation is achieved by subtracting the intra-shot bulge wave noise model from the intra-shot seismic detector signals.

Abstract: In dual-sensor, bottom-cable marine seismic exploration where hydrophone/geophone pairs are deployed on the marine bottom, coupling imperfections between the geophones and the marine bottom contribute to differences between the impulse response of the geophones and the impulse response of the hydrophones. To correct for the coupling imperfection, a filter is designed which compensates for the inherent impulse response differences as well as response differences caused by the imperfect coupling. Preferably, the filter is designed using a calibration procedure prior to production shooting. First, the response of a hydrophone and geophone to a seismic wave is recorded. Then, these recorded responses are transformed into the frequency domain. Once transformed, the response of the hydrophone is divided by the response of the geophone to produce a filtering function.

Abstract: A method of quantifying the level of weather and sea noise during marine seismic surveys which often negatively effect the acquired data produced thereby, by recording this noise along the seismic line prior to the shot registration and possibly also during a break in the shot registration and/or after the conclusion of the shot registration, and obtaining a picture of these noise conditions which correspond to those which are found in the stacked records of common reflection points for improving the signal/noise ratio in the stacked CMP data.

Abstract: Modular device for the reception, the acquisition and the transmission, to a central control and recording unit, of signals picked up by a very large number of seismic acoustic receivers distributed along a streamer of great length under water in operation.The receivers in each one of the sections (Tk) of the streamer are arranged in several groups and the receivers (H1 to Hp) of a same group are connected with an acquisition unit (U1 to Um) located close to them. All the units of each section are connected through digitized command and data transmission lines (LOC,BD) with a common memory and a transmission management unit in an interconnection box (Bk) at one end of the streamer section. Transferring a great part of the electronic equipment into the streamer sections is very favorable for the balancing of the streamer in the water, for obtaining a good signal to noise ratio and it facilitates the development and the exploitation of the material.

Abstract: An improved method and apparatus for conducting seismic prospecting is provided wherein more accurate estimates of the source wavelet can be achieved. Receivers (202) detect pulses at vertically offset locations. The pulses are converted to digital signals in a signal processor (212) and stored on a recorder (210). A processor (108) operates on the stored signals to produce an output wavelet A'(107 ,.theta.) in accord with the equation .intg.(P.G.sub.n -G.P.sub.n)dx.sub.g.

Abstract: Disclosed is a seismic surveying and data processing method to filter from seismic data any energy contributions that are not in the seismic line of profile. The surveying method requires a receiver geometry wherein at least one receiver is in and at least one receiver is out of the line of profile, so that in common offset gather or shot record plots, seismic events along the line of profile are aligned in time and out-of-plane energy takes the form of a series of sawtoothed seismic events arriving at different times in the different lines of receivers. Knowing the number of out-of-plane energies and their respective dips allows for the design of a filter, which is applied to the data with a computer, to null and thereby remove the effects of unwanted out-of-plane energy from the seismic survey data.

Abstract: An adaptive, or neural, network and a method of operating the same is disclosed which is particularly adapted for performing first break analysis for seismic shot records. The adaptive network is first trained according to the generalized delta rule. The disclosed training method includes selection of the seismic trace with the highest error, where the backpropagation is performed according to the error of this worst trace. The learning and momentum factors in the generalized delta rule are adjusted according to the value of the worst error, so that the learning and momentum factors increase as the error decreases. The training method further includes detection of slow convergence regions, and methods for escaping such regions including restoration of previously trimmed dormant links, renormalization of the weighting factor values, and the addition of new layers to the network. The network, after the addition of a new layer, includes links between nodes which skip the hidden layer.

Abstract: A method is provided for adaptive minimum-phase deconvolution. The deconvolution method removes source and receiver wavelet variations in a surface-consistent manner from traces of a seismic survey which has the traces indexed by source and receiver locations. A plurality of source-pairs and a plurality of a receiver-pairs are selected from the traces. Each source-pair has two designated sources and each receiver-pair has two designated receivers. Cross-correlations are performed on traces in each source-pair which have common receivers to provide a source-pair cross-correlation signal for each common receiver. Cross-correlation are performed on traces in each receiver-pair which have common sources to provide a receiver-pair cross-correlation signal for each common source. The cross-correlation signals of each receiver-pair and each source-pair are stacked to provide stacked cross-correlation signals.

Abstract: A method of deterministically computer generating a model of a response voltage waveform of a seismic receiver employed in a seismic, particularly marine, data gathering system, the model incorporating factors that have been identified as significant contributions to amplitude, such as directivity, divergence, attenuation, interbed multiples, and transmissivity. The model is generated from the mathematical manipulation of well log data and data gathering system characteristics into a seismic range equation, namely: ##EQU1## where E.sub.r (f)=received energy densityE(f)=radiated energy densityD(.theta..sub.s, .phi..sub.s, f)=source directivity along .theta..sub.s, .phi..sub.s direction at the sourceA.sub.c (.theta..sub.H, .phi..sub.H, f)=Capture area along .theta..sub.H, .phi..sub.H direction at the hydrophone arrayR.sub.T =target reflection coefficientD.sub.

Abstract: In accordance with the invention, there is provided a system for determining the location of an acoustic impedance boundary within the earth. A seismic signal is generated at a first location and detected at a second location so that the signal travels from the source to the acoustic impedance boundary and from the acoustic impedance boundary to the sensor. In a first embodiment, the travel time from source to receiver and the direction, in three dimensions, of the arrival path of the signal at the sensor are determined. Utilizing the determined direction of travel to the sensor and known information regarding the velocity profile of the earth strata between the source and the acoustic impedance boundary and between the receiver and the acoustic impedance boundary, a calculated travel path from the source to receiver is determined over which the calculated travel time substantially equals the measured travel time.

Abstract: In dual-sensor, bottom-cable marine seismic exploration where hydrophone/geophone pairs are deployed on the marine bottom, coupling imperfections between the geophones and the marine bottom contribute to differences between the impulse response of the geophones and the impulse response of the hydrophones. To correct for the coupling imperfection, a filter is designed which compensates for the inherent impulse response differences as well as response differences caused by the imperfect coupling. Preferably, the filter is designed using a calibration procedure prior to production shooting. First, the response of a hydrophone and geophone to a calibration wave is recorded. The calibration wave has a magnitude that is similar to the magnitude of a reflected wave that hydrophone and geophone would detect during normal production shooting. These recorded responses are transformed into the frequency domain.