Abstract: An interface module assembly for disposition between a marine tow cable and n array of acoustic receivers includes a plurality of bodies interconnected in series by flexible tethers. A proximal one of the bodies is adapted for connection to the tow cable and a distal one of the bodies is adapted for connection to the array. An external coaxial cable extends between each two of the bodies and is in communication with other external coaxial cables by way of internal coaxial cables within the bodies.

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 is disclosed to identify existence of near-surface drilling hazards in the vicinity of a sea floor location comprising the steps of: obtaining 3D seismic data for the seafloor in the vicinity of the sea floor location; preparing high resolution 3D vertical profiles from the 3D seismic data; preparing an artificially-illuminated rendered surface based on the 3D seismic data; and identifying existence of near-surface hazards in the vicinity of the sea floor location by visual analysis of the rendered surface with reference to the high resolution 3D vertical profiles. Deep tow and geohazard surveys, which are expensive and time consuming are not required in the practice of the present invention. 3D seismic surveys that are used in the practice of the present invention have often been prepared for other purposes.

Abstract: A multivariate stochastic simulation application that involves the mapping of a primary variable from a combination for sparse primary data and more densely sampled secondary data. The method is applicable when the relationship between the simulated primary variable and one or more secondary variables is non-linear. The method employs a Bayesian updating rule to build a local posterior distribution for the primary variable at each simulated location. The posterior distribution is the product of a Gaussian kernel function obtained by simple kriging of the primary variable and a secondary probability function obtained directly from a scatter diagram between primary and secondary variables.

Abstract: The invention disclosed herein is for an improved electrical connector assembly used on couplers and program modules in marine streamers used in offshore seismic exploration. In particular, the invention disclosed herein is comprised of a deformable seal ring with a plurality of holes formed therein through which pass individual conductor wires through which are transmitted signals from various hydrophones disposed along the marine streamer. Deformable nipples are disposed on each side of the seal disk 16 around each of the openings extending through the seal disk. The seal disk and nipples are deformed around the conductor wires passing through the openings in the seal disk through use of a compression disk and spring which provides dynamic spring loading of the seal disk-conductor wire interface, thereby maintaining the integrity of the seal established between those components.

Abstract: The invention centralizes data acquired through active or passive monitoring equipments installed permanently in contact with a geologic formation and notably in wells, under the control of one or several permanent stations (PCL) comprising microcomputers. The signals collected by these stations including spontaneous or induced seismic signals, parameters measured by condition sensors, etc., are converted and transferred onto a communication network managed by a server. The signals are translated into a common format more easily accessible for a seismic laboratory taking part in the processing of the data collected by the various monitoring equipments.

Abstract: A method is provided by which the presence, if any, and location of a hydrocarbon reservoir or reservoirs adjacent to a subterranean surface can be determined based on DAD values which correspond to grid points of the surface. DAD values, specifically defined herein, relate to the change in seismic amplitude (Delta Amplitude) as divided by the Dip magnitude at each grid point. According to a preferred embodiment, colors are assigned to grid points based on the sign of the DAD values, and such assigned colors are plotted onto a depth/time contour map of the subterranean surface to result in a display which clearly indicates the location of any hydrocarbons.

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: In a resistivity log, a curve is obtained showing the values of resistivity where adjacent beds impact the measured resistivity. The curve as a function of well depth is first converted into a rectangularized curve so that the interfaces of the adjacent strata are located, and by a suitable number of iterations, a correction factor is applied. The corrected rectangular log is obtained with a correction coefficient computed at each depth. For each computation, the impact of all the strata within a specified depth window is considered, while strata beyond that window are simplified by representing the strata beyond the window with single equivalent bed values to reduce the number of computations required. This then provides a resistivity log which is substantially free of shoulder bed effect.

Abstract: The device comprises instruments for collection and recording of signals in seismic exploration of the substratum off-shore. The device is designed as a pole which is adapted to be forced down into the seabed and comprises a pointed lower end (7), an intermediate approximately cylindrically shaped main portion (6), a vibration-absorbing spacer (14) between the pointed end (7) and the intermediate main portion (6). The other end of the intermediate main portion (6) is connected to a top part (8) designed for inserting/pulling and other ways of handling the device. The pointed end (7) at least comprises geophones (15-17) and a hydrophone (23) is placed in the vicinity of the upper end of the device. The majority of the device's other instruments are placed in the intermediate main portion (6). The device is connected to a main cable (4) which extends to a seismic ship (29, 31).

Abstract: A method of performing a marine seismic survey is disclosed Seismic receivers, either hydrophones or geophones, are deployed in a set of parallel lines in the survey area. The acoustic energy is generated from a conventional marine seismic source towed by a vessel traveling in paths which are substantially perpendicular to the lines of receiver stations. The paths may pass over the lines of receiver stations, and may also pass outside of the receiver area. Alternative embodiments are disclosed which include sequencing of multiple sets of receiver station lines with one another, so that shots fired along different segments of the path correspond to the different sets of receiver stations. In addition, multiple sources may be towed and alternatively fired, to improve the survey efficiency.

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: 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 of and an apparatus for the high-resolution sea bottom prospecting, in which an electroacoustic paraboloidal transducer is placed into water, the electrodes of which are near the focus of the paraboloid and are connected both to a capacitor bank the capacitance of which may be varied at will and to a supply circuit for the generation of an electroacoustic discharge between said electrodes. As the capacitance varies the delay time between the primary pulse or underwater prospecting pulse and the cavitation pulse is recorded at any discharge, and at the same time dominant frequency of the prospecting signal spectrum is determined. Afterwards capacitance values are set so as to provide both cavitation pulses the contribution of which to the resulting pulse is minimum and a dominant frequency spectrum as broad as possible.

Abstract: A submerged cable is fitted with one or more tethered transducers that are otatably supported on the cable between clamped collars spaced apart to receive a standoff device. The device has pivotably connected flat portions which define semi-circular lower parts to so receive the cable. Upper triangular panel portions can be spread apart to receive the cable, and clamped together by a clevis that is connected to a riser or tether for the transducer.

Abstract: A marine seismic bottom geophone anchor and coupling device comprising two rectangular fabric sections attached along their edges and along a plurality of lines between edges to form a plurality of pockets. The pockets are filled with a weighting material. Connecting means are provided so that when the combined fabric sections are wrapped around a marine seismic bottom geophone, it will be held in a generally cylindrical form to simultaneously anchor the geophones and associated cables at a desired marine bottom location, isolate the sensors from noise sources, and provide good coupling to the marine bottom for receiving desired seismic signals.

Abstract: A remote sensing system is provided which operates as a bipolarized, differential mode, LDI (laser differential interferometry) system to detect an electrical signal produced at a remote location. The system is adapted to reduce the effects of turbulence induced frequency fluctuations by using an array retroreflector apparatus which converts a single sensing beam into a single return beam having two, overlapping, transversely polarized sensing signals; thus, turbulence induced noise will be common mode to both return signals and cancel at the receiver.In preferred embodiments, the system is used to remotely detect an amplified array signal from a plurality of seismic detectors (e.g., geophones or hydrophones) connected to form an array at the remote location. The target is coupled to common motions at the selected location and the amplified array signal is coupled to an optical component within the target.

Abstract: Controlled phase marine seismic subarray for use in a marine seismic array and methods for constructing such subarray are provided. A controlled phase marine seismic subarrays of the present invention are arranged to operate at a preselected depth and to provide generally downgoing (for angles of emergence from the array that are of interest) far-field pulses having phase spectra that match the phase spectrum of the vertically downgoing far-field pulse up to a ghost-notch frequency. The methods select the depth of operation and type of sources for the subarray, select a maximum number of identical elements and spacing based upon the highest incidence angle and frequency for which phase control is desired, and construct a plurality of parallel, linear, subarrays.

Abstract: A marine seismic surveying system and method are disclosed. A plurality of receiver arrays, each arranged as groups of receivers (hydrophones or geophones) mounted along a cable, extend from a central location thereamong, and are connected to a platform near the central location. Systems with single and multiple platforms and their associated arrays are disclosed. The arrays each extend from the central location in different directions, preferably in a symmetrical fashion, and have their terminal ends fixed in position by way of an anchor or dynamic positioning means. Position and depth indicating instruments are also preferably mounted in each array, and at other locations in the area so that the receivers may be accurately located. The survey is accomplished by a seismic source traveling along a path which intersects the lines defined by one or more of the seismic arrays at an angle, for example a 45.degree. angle for perpendicularly deployed arrays.

Abstract: A device including instruments for use on the seabed for the collection and recording of first signals during off-shore seismic exploration.

Abstract: A new method for measurement of the directional spectra of surface gravity (water) waves. Measurements are made at a single point by orthogonally mounted seismometers buried below the seabed surface and a pressure sensor resting on the seafloor or buried below the seabed. The maximum entropy principle is used to find the directional distribution function for the waves traveling through the sediments as measured by the seismometers. This function is combined with the frequency spectra of the ocean surface waves to form the directional spectra of the surface gravity waves. The method produced high directional resolution for instruments that were adequately coupled with the seabed. The method is also capable of detecting objects moving through water, such as surface ships and submarines.

Abstract: The invention generally pertains to apparatus for determining bedload thickness of a bedload on a bed surface in an aquatic medium. An acoustic source is operative when energized for producing incident acoustic waves in the medium directed at the bed surface resulting in reflected waves. An acoustic sensor is movably locatable between the acoustic source and the bed surface and is responsive to the incident and reflected waves for producing a variable output representative of the sum of the incident and reflected waves. The sum varies between a maximum and a minimum with distance from the bed surface. A height sensor is responsive to the position of the acoustic sensor relative to the bedload thickness for producing an output indicative thereof. A processor responsive to the acoustic sensor output and the height sensor output produces an output indicative of the thickness of the bedload thickness.

Abstract: Seismic streamers (detection cables) used in the reception of reflection signals during seismic surveys at sea, where the streamer is towed behind a vessel, are constructed with an external, tubular cover (1) of a flexible plastic material. In order to reduce the noise produced by movement of the streamer through the water the external cover (1) is constructed with continuous longitudinally extending grooves (3) in its longitudinal direction, and preferably regularly disposed circumferentially around the entire periphery of the cover (1).

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: A method and apparatus for recording acoustical and seismic signals at the ocean bottom with minimal noise. A seafloor seismic recorder couples geophones to the water bottom, stores the seismic data, and is retrievable. The device is comprised of a chassis, a ballast ring, an electronics control package, a geophone package, a buoy means, and a leg extension means. The geophone package is disconnectably connected to the portion of the control package housing, so that the geophone package can remain coupled to the seafloor, when the control package and chassis rise toward the surface for a short distance. The buoy means permits the ballast ring and geophone package to become embedded in the sediment upon impact, and allows the chassis, geophone package, and control package to rise to the surface upon release of the ballast ring.

Abstract: A termination assembly is disclosed providing a substantially watertight, yet field serviceable interface to a plurality of electrical splices. The termination assembly includes a housing having an anchor portion for receiving and fixing a multi-transmission line cable therein, a ported sleeve for cradling the transmission lines, and a shell for providing field access to the splices between the transmission line in the interior of the housing. A resinous epoxy, together with O-ring seals and heat shrink tubing provide redundant protection against the invasion of water into the housing along the transmission lines.

Abstract: In towing sources of seismic energy behind a vessel, especially in connection with seismic surveys in waters which are covered with ice, the buoyancy floats and also the sources of seismic energy are readily influenced by broken up ice collecting behind the icebreaking towing vessel. In order to stabilize the tow of sources of seismic energy a towing line (7) is secured between the buoyancy means (4) belonging to the tow of sources of energy (3) and the vessel (1) at a point (10) which is located in the area of the waterline, so that towing line (7) will extend in the area of the waterline. Another towing line (8) is connected directly with the array of sources of seismic energy (5) and is secured to a towing point (11) on the vessel (1) located below the waterline. An arrangement is also disclosed for securing the towing line (8) in a suitable location to avoid influence from ice and, furthermore, the design of floats (4) avoids influence from the ice.

Abstract: Methods for the construction of and controlled phase marine source arrays provide phase control for source array pulses radiated into emergence (or incidence) angles of interest. Phase control means that the phase spectra associated with source array pulses radiated in a generally downgoing direction, (i.e. for angles of emergence from the array that are of interest) will match the phase spectrum associated with a vertically downgoing source array pulse out to the "ghost-notch" frequency associated with the vertically downgoing pulse. Although the range of emergence angles over which phase control is possible may be limited by the array geometry, proper attention to and control of array geometry and the radiation characteristics of the individual array source elements provide such controlled phase marine arrays.

Abstract: In seismic surveys in waters covered with ice, where seismic impulses are actuated under water and reflected signals are detected by a streamer cable (2) towed behind a vessel (1), in order to avoid the source of noise located outside the seismic system due to the icebreaking operation of the vessel (1) the vessel (1) is stopped during active survey and the streamer cable (3) is hauled in with a speed corresponding to the desired propulsion speed of the cable during detection. After detection the vessel again resumes ordinary operational speed and the streamer is paid out with a speed which maintains the desired advancing speed of the system.

Abstract: A vertical hydrophone array and a system of multiple arrays are disclosed. The vertical hydrophone array includes multiple groups of hydrophones mounted along a cable. A floatation device is coupled to the cable at one end, and an anchor is coupled to the cable at another end via a remotely controllable release. Depth transducers and position transponders are preferably mounted along the cable to provide precise depth and position indication to the surface. The release allows for retrieval of the array while leaving the anchor behind, thus reducing the potential for array damage. In the system including multiple arrays, a central positioning anchor is disclosed, through which tensioning cables pass. Each tensioning cable is connected to the float end of a vertical array, so that tension of the tensioning cable allows for control of the angle of the sensor array from the vertical. A clamp is preferably provided so that the position of the array may be held without maintaining tension thereon from the surface.

Abstract: The present invention includes a buoy floating on a body of water. Positioning devices attached to the buoy are responsive to control signals to control the position of the buoy. A hydrone is suspended from the buoy to a predetermined shallow depth with an electrical cable and converts seismic waves to an electrical signal. A navigational device, on the buoy, provides position signals corresponding to the position of the buoy. A first transceiver with an antenna, receives first transmitted signals from a ship and provides them as control signals to the positioning devices. The first transceiver transmits signals corresponding to the seismic signal and to the position signals. A seismic device, located in the body of water, creates event in the body of water in response to a fire signal. Fire control apparatus located on the ship provides the fire signal to the seismic device.

Abstract: An underwater sensing arrangement in which hydrophones are embodied in horizontally disposed arms of a hydrophone support structure adaptive to be suspended below the surface of the water and in which the support arms are elliptical and orientated so that they present the lowest resistance to horizontal flow of water past the structure and present the highest resistance or drag against movement.

Abstract: A method in real time control systems for seismic interference to indicate an acceptable level of interference in relation to the amplitude, angle of incidence, and frequency of a seismic reflection signal, and to remove such interference loaded signals during seismic surveys, comprises steps to determine lower threshold values of coverage, identify interference and amplitude anomaly in the recorded signal of reflection, estimate the expected value of amplitude characteristic of the signal on the basis of recorded amplitude characteristics of recorded signals from one or a plurality of preceding series of survey, mark time windows in which interference and/or amplitude anomaly are identified, generate a table of the number of times a certain time window was marked in the series of recordings of the same point of reflection, assign limits on the number of interference events to various marked time windows, and remove from the recordings those time windows wherein the number of interference events exceeds the l

Abstract: A marine seismic cable network including cables towed parallel to the surface of the sea at at least two depths for providing time analysis of reflected seismic data to dimensionally clarify characteristics of reflecting surfaces.

Abstract: A piezoelectric sensor comprising at least one pair of flexible sensitive elements of great length whose respective electrodes are connected in parallel. The interconnection is provided by interlacing the sensitive elements so that the two electrodes of each of the flexible sensitive elements are alternately in electric contact with the two electrodes of at least one other sensitive element. The sensor may be formed by winding at least one pair of sensitive elements on a support in two spirals of opposite directions with interlacing. The chosen assembly method provides both good mechanical strength and simplifies the electric connections because of the multiple electric contacts between the electrodes.

Abstract: A marine acoustic array employs a plurality of sections connected together sequentially with the outer surfaces of said sections having a non-smooth configuration to create a water flow along the length of the array as it is towed through a water layer that causes sensors within the array to provide outputs having improved signal-to-noise ratios.

Abstract: A method of acquiring seismic data is disclosed which includes a horizontal towed receiver array in conjunction with at least one vertically oriented receiver array formed from a plurality of receiver elements spaced apart vertically within a plurality of cable. By simultaneously recording the data from both arrays, seismic data can be acquired for locations directly beneath a fixed obstruction, which a towing vessel has had to steer around.

Abstract: A method is disclosed where acoustic pulses are used to calculate the velocity of the medium. The inventive aspect of the invention is that the acoustic velocity may be calculated without initially knowing the separation distance between the source and the distant receivers. The method utilizes established geometrical relationships which may be solved to produce the velocity. The velocity is often used to calculate the separation distances between the desired points.

Abstract: A method for conducting a three-dimensional subsurface seismic survey utilizing a plurality of seismic receivers arranged in an orthogonally uniform pattern is disclosed. A predetermined pattern of shotpoints is arranged such that every point in the surface area of interest is sampled over a desired range of offsets and a full range of azimuths. The utilization of shotpoints outside the pattern of receivers allows examination of a subsurface area which is greater than the area of the pattern itself. The output of each receiver in the pattern is simultaneously recorded for seismic energy applied to the surface of the earth. Where the area of interest is quite large, a multitude of patterns of seismic receivers may be utilized to ensure coverage of the entire area. In a marine application of the present invention a plurality of seismic receivers are arranged in an orthogonally uniform pattern under a body of water or by utilizing multiple parallel marine streamers towed by one or more tow boats.

Abstract: A procedure for surveying the seismic data of a region comprising a central body or structure, for instance an island, by means of a ship-towed streamer, wherein the ship follows a spiral path (2) around the central structure (1) to collected seismic data. Preferably the spiral is an Archimedean spiral with equidistant individual spiral line segments (7, 8, 9).

Abstract: Walkaway vertical seismic profiling is conducted in a body of water. A marine seismic cable is positioned substantially vertically in a body of water. The cable has a number of hydrophones spaced along its length. A seismic source is moved along a line of traverse past the seismic cable and is periodically activated to emit acoustic waves. The response of the hydrophones to reflection of the acoustic waves from subsurface formations is then recorded for processing and analysis.

Abstract: A method of measuring the shear modulus profile of a seabed floor using one or more bottom shear modulus profilers, each having a seisometer package to measure the seabed motion in three dimensions and a sensor for measuring the pressure at the seabed floor, placed on or below the seabed floor, and a means for converting the measurements derived therefrom into a shear modulus profile.

Abstract: A method of marine seismic exploration of the strata beneath a body of water comprising the steps of generating a compressional wave in the body of water and sensing the converted shear waves reflected from the strata.

Abstract: A tubular piezo-electric sensor has at least one sensitive element disposed against an outer surface of a tubular support. A substance whose acoustic impedance is very different from that of the material forming the tubular support is disposed therein and a remaining volume of the tubular support is filled with liquid. Glass fiber cords or open cell foams, for example, are used as the substance, and the liquid may, for example, be that which fills a seismic streamer and, in this case, the tubular support is left open. The tubular support may also be closed at both ends by sealed caps and included in a protective sheath. The dimensions of the tubular support and the material from which it is made are chosen so as to optimize the sensitivity of the piezo-electric sensor.

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: The novel method substantially reduces the pressure pulse, generated by a first radial motion of a body of water, by changing the radial motion into axial action. The change from radial motion into axial motion is produced by generating a second radial motion of opposite phase within the body of water.The method can be used to substantially reduce the pressure pulse, generated by the implosion of a body of water, by generating an explosion in the body of water. It can also substantially reduce the pressure pulse generated by an explosion within a body of water, by generating an implosion of the body of water. The method can further be used to generate within a body of water an impulsive acoustic signal by sequentially generating within the body of water a first explosion and a second explosion. The apparatus comprises a signal chamber which contains a first charge of gas. A normally-closed valve maintains the signal chamber closed and has a discharge port into the water.

Abstract: A procedure for seismically surveying a region, in particular a marine region, wherein objects such as drilling platforms (1,2,3) prevent surveying by conventional seismic means such as towed streamers. In the invention, the total region first divided into sub-regions (5,6,7) wherein receiver chains (4) are stationarily mounted between two of the objects. A sound transmitter is the moved relative to the chain of receivers along a grid as the transmitter is repeatedly, periodically activated. Data collected by the receivers are recorded for each sub-region and the completely surveyed sub-regions are combined by grid transformation to construct a uniform three-dimensional data volume.

Abstract: System for seismic profiling of structures (2) beneath the sea bottom, comprising an acoustic transducer array (12) which synchronously and coherently generates an acoustic wave adapted to be reflected from said structures (2). When the reflected acoustic waves propagate towards the water surface (1), there is caused a perturbation of the electromagnetic reflection coefficient thereof. Receiver means for detection and characterization of the received acoustic field at the surface (1), comprises a radar system (10) illuminating the region concerned of the surface (1) and imposes thereat a number of interferograms each corresponding to the acoustic field from a scattering point given by the position thereof and the frequency of the field. By recording the degree of coincidence between the interferograms and the acoustic perturbation pattern on the water surface (1), the seismic properties of said structures (2) are surveyed.

Abstract: A float for use in seismic surveys of the sea bed supports a plurality of seismic pulse transmitters (6) which are suspended on lines (7) beneath the float (1). At a distance from the front end of the float (1), on one sidewall thereof, a fastening device for a towing cable and a lead-in for control lines and lines for supplying operating medium to the pulse transmitters are provided. These lines and cables are gathered in a common line (3) which extends behind the tow ship. The line (3), at a distance away from the float (1), is connected to a line (4) which leads to a length-regulating device (12) inside the front section of the float. The float is also provided with at least one motor (10) with a drive shaft (9)leading to hoisting drums (8) for the lines (7) to the respective seismic pulse transmitters (6). Both the motors (10, 12) and the seismic pulse transmitters (6) are connected to the pneumatic supply line.

Abstract: A marine geophysical prospecting system employs a hydrophone streamer cable containing electromagnetic field sensors, modified to be towed at a preselected distance above the sea floor by a first marine vessel senses electromagnetic energy from selected substrata beneath bodies of water. The voltage between sensors may be amplified by amplifiers in the cable or by amplifiers aboard the towing vessel. Optionally, a second similarly modified cable is preferably located above the near-bottom cable. Both cables may also contain hydrophones and/or accelerometers, as well as depth and position sensors. Optionally, a second vessel tows at least one conventional seismic source to create compressional energy which propagates downwardly through the water into the substrata beneath the body of water. At appropriate porous subsurface formations, the acoustic energy is converted to electromagnetic energy.