Abstract: A method for attenuating coherent and incoherent noise in seismic signal data is provided. Seismic signal data is transformed from a time-space domain using a Radon-transform domain. In the Radon-transform domain, coherent noise is attenuated by muting and incoherent noise is attenuated by diversity stacking. Data remaining in the Radon-transform domain in transformed back to the time-space domain by an inverse Radon transform.

Abstract: An encoded seismic source, such as a marine vibrator, and a receiver, such as a seismic streamer, are pulled through water at constant velocity and depth. The source is periodically actuated and the reflected acoustic signals are converted by the receiver into seismic data. The seismic data are transformed to a fixed reference frame relative to earth before being processed.

Abstract: Marine seismic data is gathered using a cable towed behind a cable having a slanted orientation in the water. The recorded data is processed to remove the time offset in the recorded data of seismic signals arriving at the cable at varying plane wave angles. In a preferred embodiment of the invention, the recorded data is then processed to align the primary signals, thereby misaligning the ghost signals. The data is also processed to align the ghost signals, thereby misaligning the primary signals. The two resulting data sets may then be summed.

Abstract: In a marine seismic survey, a method for measuring the acoustic properties of the water mass at each seismic station along a line of survey by recovering acoustic reflections from discrete discontinuities within the water above the water-bottom reflection. A profile of the velocity distribution within the water column is calculated from a conventional velocity analysis.

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(l.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: Methods are provided for processing seismic data acquired during marine seismic operations when the seismic streamer cables or sources deviate from their desired acquisition track. The method of the present invention initially processes the data using conventional normal moveout techniques, then applies conventional dip moveout techniques, followed by regularization of the cross-line data, and then 3-D migrating the regularized data. Regularization involves determining the signals at preselected cross-line positions based upon the signals detected and recorded at the measured cross-line CMP positions.

Abstract: A digital marine seismic system employes a plurality of data acquisition control modules which simultaneously digitize analog seismic signals. The control modules also are selectably addressable in that each module is uniquely programmed to respond only to a particular control word. The system allows a large number of channels, such as 480 channels, on a simple transmission system, such as a twisted pair of wires. Each module includes a power switch to sequentially apply power to downstream modules. Selective addressing of the switches allow testing of specific modules for power malfunctions.

Abstract: A processing method is disclosed for marine seismic surveying which utilizes two vertically spaced marine streamers each having a plurality of seismic detectors contained therein. A seismic energy source positioned at or near the surface of a body of water is utilized to generate seismic waves which propagate into earth formations below the water and reflect back up to be detected at each streamer. Seismic waves also reflect from the water/air interface back down toward the streamers and must be separated from the upgoing seismic waves to enhance the accuracy of the resultant trace. The seismic waves detected at two selected vertically displaced seismic detectors are combined to form a sum signal which is then combined with a scaled time integral of a difference signal to form a resultant signal which preserves either the upgoing or downgoing seismic waves.

Abstract: Coherent noise on seismic records is suppressed by reformatting the common shot gathers to common receiver gathers. Pairs of seismic traces from a common receiver gather are corrected for differential normal moveout, weighted in inverse relation to the RMS signal power, and combined to generate compressed common receiver gathers. The compressed common receiver gathers may be reformatted as common midpoint gathers for further processing.

Abstract: A marine seismic reflection prospecting system attenuates coherent noise through reinforcement of primary reflection data by the addition of corrected ghost reflection data. The system includes a seismic energy source, a detector, a wavefield separator, a time-shift element, and an element for generating an output signal representative of an additive linear combination of time-aligned primary and ghost signal components. The system's output is suitable for further pre-stack processing, e.g., NMO correction.

Abstract: The level of signal noise caused by fluid flow at a pressure transducer, such as a hydrophone or geophone, is determined by measuring the electric field induced when the fluid flow through a magnetic field. The electric field, which is proportional to flow rate, is measured by electrodes positioned about the transducer. The pressure due to the flow is derived from the flow rate voltage by a digital filter which may be adaptive, to allow for varying flow conditions, or which may employ a predetermined electric field/flow noise relation. This flow noise is then subtracted from the received signal, the resultant signal then being substantially noise free.

Abstract: An inventive method for simultaneously collecting depth-of-focus vertical seismic profiling (VSP) data and three-dimensional surface seismic data is disclosed. At least one seismic sensor is deployed at a predetermined depth of a borehole and raised in increments determined by the survey. A seismic source and a plurality of seismic sensor may be deployed at the surface along a partial arc offset from the top of the borehole by a distance inversely proportional to the depth of the sensor in the borehole. The seismic source generates a seismic signal at a plurality of points in a circular path around the borehole. Once a circle has been completed, the borehole sensor is raised, and the seismic signal generator and sensors are moved to the next largest circular path and the process is repeated. The seismic signals are simultaneously recorded by the borehole sensor and the sensors deployed in the arcuate path.

Abstract: A common bandwidth determination method for two disparate seismic datasets includes developing a weighted average of first least-squares filters assuming the data from the first dataset is the input and the data from the second dataset is the desired output, developing a weighted average of second least-squares filters assuming the data from the second dataset is the input and the data from the first dataset is the desired output, determining a first transfer function from the first weighted average filter design and a second transfer function from the second weighted average filter design, plotting respective amplitude and phase spectra using each of the first and second transfer functions, plotting the product of the amplitude spectra and the sum of the phase spectra and determining the common bandwidth where the amplitude spectra is one and the phase spectra is zero.

Abstract: The invention is a method of reducing phase distortion in a detected seismic signal resulting from Doppler shifting of the transmitted signal. An operator is convolved with the seismic data to correct the dispersion. The operator is determined for the particular transmitted signal and boat speed. The operator is normally determined in the frequency-wave number domain. The seismic data may be transformed to the frequency-wave number domain for performing the convolution. The transformed data may then be transformed back to the time-space domain. Alternatively, the determined operator may be transformed to the time-space domain and the convolution performed in that domain.

Abstract: A two stage, decentralized device for transmitting seismic data information from seismic receivers of a seismic streamer to a central recorder on a ship, including a series of interconnected sections each having a plurality of seismic receivers distributed over it's length, seismic signal acquisition apparatus for digitizing and storing seismic signals coming from a group of seismic receivers to which a respective seismic signal acquisition apparatus is connected, central control and recording device on the ship and assembly of electronic modules each disposed in the vicinity of a seismic receiver and being capable of amplifying and filtering the seismic receiver signals.

Abstract: The present invention relates generally to a method and system for the real-time processing of seismic signals collected with multichannel seismic systems and to a stand-alone system for verifying the quality of such seismic signals so as to quickly and accurately determine if the acquisition parameters established for the multi-channel seismic system are producing interpretable seismic data. More particularly, a method for obtaining surrogate seismic signals representative of a multichannel set of seismic signals acquired with a marine exploration system and a measure of their quality are provided.

Abstract: At least two methods of reconstituting the original form of a time/amplitude trace, such as seismic data, are disclosed wherein the seismic data has been rectified by a scanner to produce a signal representative of a hardcopy display of the trace. One of the methods comprises selecting a time window of a certain duration, obtaining a measurement of the predominant period within the selected positive components of the signal, and filtering the signal with a bandpass filter having a range of about F/2 to about 3F/2, where F equals the reciprocal of the predominant period of the signal.

Abstract: A seismic prospecting method comprising the use of at least two vehicles for moving an acoustic wave emission assembly and a reception assembly such as a seismic streamer. The method consists in performing successive cycles of emission of acoustic waves, of reception and of recording of the acoustic waves coming from reflecting interfaces of the subsoil and combining the recording so as to provide multiple coverage. The vehicles follow paths such that the angle formed by the respective advancing directions remains greater than or equal to 90.degree. in absolute value.

Abstract: A processor responsive to multiple AC analog signals has individual sampling circuits to sample and hold each AC analog signal in DC form. After the DC signals are multiplexed, a single error correction circuit calculates correction voltages individualized for each sampling circuit and sums them with the DC signals. An instantaneous floating point amplifier amplifies each signal in 12 db increments up to a preselected limit, and then a second sampling circuit holds the amplified signal before an analog-to-digital converter generates a digital signal representative of the amplified signal.

Abstract: A method of underwater seismic testing is disclosed which does not require the use of long hydrophone streamers and which dispenses with the conventional CDP stack technique. The method enables signal processing to commence as soon as the first shot has been fired. The method involves traversing the region of interest with a survey vessel while firing a single seismic source repeatedly and observing the sub-sea response to the repeated shots using a single seismic receiver to provide thereby single-trace data which is then processed to generate the required sub-sea geological data. The signal processing may be effected in two stages, the first being deconvolution and the second being "3-D" imaging, preferably using the Kirchoff integral formulation.

Abstract: A method for attenuating multiples in common depth point data whereby common depth point data is received and spike deconvolution maybe performed on the data. The data is constant velocity stacked and gap deconvolution is performed. The primary stack velocity is determined and all data having a velocity other than the primary stack velocity is muted. All scans within the constant velocity stack are composited. These composites are arranged in proper order and displayed.

Abstract: The present invention indicates that in exploration of permafrost regions of the world for oil and gas accumulations, flexure noise can be attenuated by careful placement of the vibratory source vis-a-vis the receiver array during collection of the Vibroseis.RTM.-type data. If the explorationist adopts a survey strategy in which the vibratory source is separated from the receiver array by a pressure ridge or its equivalent over the ice formation of the region under survey, then - surprisingly - the seismic reflection signals can be easily collected and displayed. Result: continuity of events from onshore reflectors can be easily followed offshore through the transition zone into deeper sea ice regions. He is aided in formulating his exploration strategy by the use of aerial and/or radar photographs or LANDSAT unmanned satellite data for mapping the pressure ridges of the area under survey.

Abstract: An analog-to-digital converter for use in seismic data processing applications is disclosed which features variants on delta modulation and delta-sigma modulation methods. A series of single bits is output by an analog-to-digital converter based on comparison of a predicted analog signal with the actual analog signal. A low pass filter and subsampling operation is applied to the output digital bits to provide digital words corresponding to the analog signal amplitude. Plural integrator stages are shown which allow reduction of quantization error.

Abstract: The present invention indicates that in exploration of permafrost regions of the world for oil and gas accumulations, flexure noise can be attenuated by careful placement of the vibratory source vis-a-vis the receiver array during collection of the Vibroseis.RTM.-type data. It has been surprisingly found that if the explorationist adopts a survey strategy in which the vibratory source is separated from the receiver array by a pressure ridge or its equivalent over the ice formation of the region under survey, then the seismic reflection signals can be easily collected and displayed. Result: continuity of events from onshore reflectors can be easily followed offshore through the transition zone into deeper sea ice regions.

Abstract: A method of determining source and receiver statics in a marine exploration area overlying a near surface low velocity layer employing a marine vessel for towing a seismic energy source and a marine detector cable, and an on-bottom seismic energy source and seismic detector located at an offset from the marine seismic line of exploration. The towed seismic energy source generates a seismic reflection signal for detection by the towed marine detector cable and a seismic refraction signal to be detected by the on-bottom seismic detector. The on-bottom seismic energy source generates a seismic refraction signal for detection by the towed marine detector cable.

Abstract: A method for optimizing the acoustic signal-to-noise ratio during a useful maximal-length recording cycle within the time frame of a minimal-length recording episode. To implement the method, during an intermittent-tow seismic operation, the noise level due to cable manipulation during an entire recording episode is monitored. A quiet-window of a desired length is established by adjusting the length of the interval during which the seismic cable is at rest. The initiation of a recording cycle is adjusted relative to the quiet window to take maximum advantage of the quiet period.

Abstract: A method is disclosed for determining if sign-clipped variations of full-waveform traces can be used in subsequent cross-correlation processing without undue hardship. In accordance with one aspect, the present invention examines skewness of the amplitude spectrum of the full waveform. If the former significantly differs from conventional Gaussian distribution over the frequency range of interest, i.e., the amplitude spectrum is non-Gaussian, sign-clipped versions thereof can be used in subsequent cross-correlation processing without undue loss in processing accuracy. In another aspect, the present invention is used to edit a series of traces, one at a time, gathered by a large multichannel collection system. In this aspect, the different spectral noise estimates, including cross-correlation estimates generated from sign-clipped versions of the full-waveform traces, are advantageously used.

Abstract: A method for eliminating ghosts, or reflections from the air/water interface of a body of water, from seismic signals detected at a predetermined depth is provided. The method employs both a pressure sensor and a motion sensor. A seismic signal and its corresponding ghost signal detected by a pressure sensor is filtered as a function of depth of the sensor to provide a preselected amplitude and zero phase shifted band-limited spike signal at an arrival time corresponding to the arrival time midway between the seismic and ghost arrival times. Similarly, a seismic and ghost signal from a motion sensor is filtered as a function of depth of the sensor to provide a band-limited spike having an arrival time midway between the seismic and ghost arrival times. The filtered motion and pressure spikes are added together in proportion to their respective signal-to-noise ratios.

Abstract: A method and apparatus for use in marine seismic data gathering comprises a vessel (1) is equipped for deploying and retrieving trailer cables and tows a plurality of cables (3) which are provided with at least one array of transmitters (5), which array constitutes a point source for a transmitter, and an acoustic cable, over the region to be investigated. The transmitter cables (3) are caused to become distributed laterally in relation to the tow direction, the distance between them, the firing power and firing timing being controlled from the vessel in accordance with data collected previously regarding the nature of the sea bed. The point source-formed transmitter arrays can be distributed both laterally and longitudinally in relation to the tow direction. The transmitter cables (3) are distributed laterally with the aid of otterboards (8).

Abstract: A method is provided of ascertaining the far field signature of an array of sound source units, each of which is small compared with the wavelength of the highest frequency of interest. The units are fired so that the interactions between them is negligible. This is achieved by firing the units sequentially so that each generates all its significant radiation before the next is fired, and/or by firing more than one unit at a time and separating the units by at least one wavelength of the lowest frequency of interest. The far field signature of each unit is measured by a pressure-sensitive detector close to the unit but in a region where the phase spectrum of the pressure field is independent of azimuth and range. The far field signature of the array is derived from the measured signatures by summation.

Abstract: A method, when practiced, enhances seismic data so as to suppress noise in the seismic data. The seismic data was generated in a conventional manner by at least one receiver apparatus whose position does not substantially change. The method includes combining at least two elementary seismograms to form noise seismograms containing little or none of the desired signal. The number of different noise seismograms so derived is at least equal to the number of elementary seismograms to be combined to form a final seismogram. The probability distribution of noise is determined for each trace of the noise seismograms from the probability distributions of noise in the traces of the noise seismograms. The most probable form of the desired signals is derived from the probability distribution of noise in the traces of the elementary seismograms to provide the enhanced seismic data.

Abstract: A method for improving signal-to-noise ratio in seismic surveying. It involves generating a series of seismic charges at time spaced intervals but at the same location. A single record is made having a time duration sufficient to cover the maximum reflection time of interest plus the total time for the series of charges. And, thereafter, the record is processed by Fourier transform of the single record to the frequency domain and by constructing frequency domain representation of the series of time intervals plus using the latter to superimpose frequency domain representations of the seismic signals resulting from each of the seismic charges. Then the processing includes inversely transforming the superimposed frequency domain representations back to the time domain.

Abstract: A method of producing a seismic signal indicative of the substrata beneath a body of water comprising the steps of: supplying acoustic energy to the body of water; sensing at a predetermined depth the pressure wave reflected from the substrata beneath the body of water and the secondary pressure wave caused by a secondary reflection of the pressure wave from the air-water interface and generating a first signal indicative thereof; sensing at the predetermined depth the particle velocity of the water accompanying the pressure wave reflected from the substrata and the secondary pressure wave and generating a second signal indicative thereof; filtering the second signal such that portions of the second signal that have a frequency that is less than a first frequency are attenuated by the filtering to generate a third signal, the first frequency being less than a second frequency which is equal to the wave propagation velocity of the body of water divided by two times the predetermined depth; and combining the fi

Abstract: A device for the sequential transmission of information elements from a sensor arrangement receiving acoustic waves at different locations and a system for recording or processing these information elements. The device includes means for generating information signals representative of the instant of reception at one of said sensor means of a directly transmitted acoustic wave emanating from a source, in the form of at least two discrete values of a continuously varying voltage which begins to be generated at the instant of reception of the direct wave, and means for determining the instant of reception from said discrete values are provided, after their transmission to the recording or processing system by a sequential transmission of the discrete values.

Abstract: A method of seismic exploration by which substantially plane or substantially cylindrical seismic energy waves are simulated by combining reflectional signal traces of conventional spherical seismic waves. Seismic sources and receivers are established in sets at positions such that at least one of the sets includes a plurality of positions spaced over an extent of the area being explored having either one or two dimensions which are large relative to a seismic energy wavelength. Seismic energy is imparted into the earth from the sources and signals are generated in response to seismic energy received at the receivers. The generated signals are then combined into a form simulating the reflection response of the earth to seismic energy having a substantially continuous wavefront in either one dimension, simulating a cylindrical seismic energy wave, or two dimensions, simulating a plane seismic wave.

Abstract: High resolution, high penetration marine seismic stratigraphic system wherein a slanted cable comprising spaced-apart hydrophone arrays gather seismic reflections so that the corresponding primary and ghost reflections from a common interface gradually are spaced apart. The primary reflections are time aligned and stacked. The ghost reflections are phase reversed, time shifted and time aligned to coincide with the time aligned primary stack and then stacked to give a combined primary and ghost stack, which effectively includes almost twice the information as from the primary stack alone. No inverse notch filters are needed to correct for the ghost phenomenon. Focused noise out of the vertical plane is also virtually eliminated.

Abstract: A seismic data generation and collection system is described for use in a exploration vessel for determining the subsea structure of the earth. A plurality of acoustic energy sources are towed behind the boat and acoustic waves are emitted therefrom by conventional means. The reflection at the subsea interfaces of the acoustic waves are picked up by the energy detectors which produce analog signals. These analog signals are then converted to digital data; multiple computers are used to reformat the data into a desired format. A real time monitor computer and monitor plotter may also be provided to assist the operator in evaluation of the operation of the system. The desired record format includes header information relating to the parameters under which the seismic shot was made, which may be written directly onto the magnetic tape containing the seismic data.

Abstract: A method of seismic exploration comprises transmitting waves from transmission sources into the medium to be explored and picking up signals in a receiver and recording these as traces, the signals being produced by reflection in the medium, the sequential transmission of the sources taking place at intervals less than the reflection time of the longest transmitted waves, the repeated transmission of any one source taking place at intervals at least equal to the said reflection time and therein being an intercorrelation function of a series of transmission instants of all the sources and a series of transmission instants of any one of the sources to give a relationship between the maximum peak amplitude and the secondary residue amplitude greater than a predetermined value and grouping the recorded traces corresponding to the same reflection point, adjusting the traces in relation to the associated source providing the information relating to the reflection point and adding together the adjusted traces relati

Abstract: A multi-purpose seismic transducer includes a first seismic sensor having a first transfer function. A transfer-function shaping filter is coupled to the output of the first seismic sensor. The filter is adjustable to shape the first transfer function to match a plurality of different second transfer functions.

Abstract: A differential amplifier circuit comprised of two operational amplifiers for use as a differential output and differential input amplifier for any two-terminal impedance transfer function. The input impedance is very low between the two input terminals, yet it is very high between either input terminal and the common or ground terminal, thus giving this amplifier many of the desirable characteristics of a transformer-coupled amplifier. High common mode voltage rejection ratios can be achieved even when moderate differential imbalances exist in the input and feedback networks due to the unique balancing feature of the circuit.

Abstract: A seismic amplifier for use in marine seismic survey work involving the transmission of signals from remote signalling stations over cable pairs to signal processing equipment. These signalling stations are comprised of capacitive transducers. The seismic amplifier of the surveying system includes operational amplifiers electrically interconnected with a feedback circuit comprised of a balanced resistive-reactive network which is a lumped parameter equivalent circuit of the transmission line and capacitive transducer. The lumped parameter equivalent circuit used for feedback provides a flat, zero-phase shift overall response over the cable pair from the transducer to the output of a differential amplifier stage which is connected to the operational amplifier outputs to improve common mode rejection.

Abstract: This disclosure deals with measuring either discontinuous or continuous impedance transitions in various media to identify or delineate the properties and nature thereof by transmitting radiant energy waves to such media to produce reflected waves therefrom, deconvoluting the outgoing and returning waves, and integrating the resulting reflection impulse-response function so as to enable appropriate interpretation of the resulting display for identification and related purposes.