Abstract: A method for operating marine seismic vibrators includes towing at least a first and a second marine seismic vibrator in a body of water beneath the hull of a vessel. At least a third marine seismic vibrator is towed at a selected depth in the water other than beneath the hull of the vessel. The at least first, second and third vibrators are operated to sweep through respective frequency ranges. The first and second frequency ranges have lowermost frequencies and uppermost frequencies respectively differing by a selected sub-harmonic frequency range. The third frequency range has a lowermost frequency at least equal to the uppermost frequency of one of the first and second frequency ranges and traverses a seismic frequency range of interest.

Abstract: A seismic vibrator has a base plate with at least four isolators isolating a frame from the base plate. Each of these isolators is offset from the plate's footprint on shelves to free up area on the plate's top surface. An accelerometer disposed directly on the base plate detects the acceleration imparted to the plate. To reduce flexing and bending, the plate has an increased stiffness and approximately the same mass of a plate for a comparably rated vibrator. The accelerometer disposes at a particular location of the plate that experiences transition between longitudinal flexing along the plate's length. This transition location better represents the actual acceleration of the plate during vibration and avoids overly increased and decreased acceleration readings that would be obtained from other locations on the plate.

Abstract: A marine seismic source comprises a housing having a central axis, an open end, and a closed end opposite the open end. In addition, the seismic source includes a piston extending coaxially through the open end of the housing. The piston is adapted to axially reciprocate relative to the housing. Further, the piston has a first end distal the housing and a second end disposed within the housing.

Abstract: The device hereof is most preferably an improved performance air gun as sound source for marine seismic exploration for petroleum deposits and it most generally is comprised of, an elongated cylindrical housing bored from each end to a fixed radial wall separating the two bores. The fixed radial wall having a through bore for hollow shaft of air control and release shuttle assembly to reciprocate within. The wall having fixed groove for elastomer shaft seal rings to seal around outside diameter of shuttle shaft and drilled passages for water entry to lubricate shaft seals. Air control end of shuttle assembly having set and release flange and internal bearing. Air release end of shuttle assembly cup shaped air release flange with bearing around outside diameter and seal means. Air control end of cylindrical housing having end cap drilled for air input means. The Air control end cap having bolt on shuttle support shaft with piston rings air input means air valving means and orifice means.

Abstract: A method for attenuating out of band energy emitted from a seismic source used in a marine seismic survey. The method includes disposing the seismic source in a body of water and releasing a gas into a volume of water surrounding the seismic source. The released gas may be configured such that it displaces the volume of water surrounding the seismic source at a rate less than 2.9×106 cubic-meters per cubic-second.

Abstract: A seabed seismic source apparatus includes a control module adapted for deployment at a seabed. The control module has a receiver for receiving a remote signal and a firing controller for generating a firing signal in response to the remote signal. The seabed seismic source apparatus further includes at least one seismoacoustic source module adapted for deployment at the seabed with the control module. The seismoacoustic source module has a seismoacoustic source for generating a seismic signal and a firing device for firing the seismoacoustic source to generate the seismic signal. The seabed seismic source apparatus further includes a transmission link between the firing controller and the firing device, wherein the firing device fires the seismoacoustic source upon receiving the firing signal generated by the firing controller.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: A method for obtaining seismic data is disclosed. A constellation of seismic energy sources is translated along a survey path. The seismic energy sources include a reference energy source and a satellite energy source. The reference energy source is activated and the satellite energy source is activated at a time delay relative to the activation of the reference energy source. This is repeated at each of the spaced apart activation locations along the survey path to generate a series of superposed wavefields. The time delay is varied between each of the spaced apart activation locations. Seismic data processing comprises sorting the traces into a common geometry domain and replicating the traces into multiple datasets associated with each particular energy source. Each trace is time adjusted in each replicated dataset in the common-geometry domain using the time delays associated with each particular source.

Abstract: A marine vibrator that in a particular embodiment includes a substantially elliptically shaped outer shell, a driver having a first and second end, at least one outer spring connected between the first end and the second end of the driver, and at least one inner spring connected between the first end and the second end of the driver. One or more masses are attached to the inner spring. At least one transmission element connects the outer spring and the outer shell. The outer and inner springs and the masses attached to the inner spring are selected to generate a first resonance frequency and a second resonance within the frequency range between 1 Hz and 300 Hz.

Abstract: A 4D seismic source comprising a series of sub-arrays of guns on flotation devices. Each flotation device has a GPS device. For firing, the guns in the e.g. three sub-arrays identified as being closest to the desired firing location are selected.

Abstract: A marine seismic source method capable of retaining low frequencies is disclosed. One embodiment of the method comprises a seismic source that generates an up-going wave and first down-going wave with opposite polarity. The up-going wave reflects off the ocean surface as a second down-going wave having the same polarity as the first down-going wave and the first and second down-going waves combine substantially in-phase to form a third down-going wave. A source apparatus to accomplish the method is also disclosed. One source apparatus embodiment comprises a device wherein at least part of the device is below the surface of the water and the device is adapted to cause oscillations below the surface of the water, and means for oscillating the device in the water to create an up-going wave and a first down-going wave and the up-going wave has reverse polarity relative to the first down-going wave.

Abstract: A seismic acquisition system comprising a remote-controlled buoy for conducting seismic acquisition operations. The buoy comprises an operating system for operating a seismic wave production device on the buoy, a placement system, a communications system, and dynamic position locating system. The seismic acquisition system also comprises a remote control system for controlling the buoy systems. The seismic acquisition system also comprises receivers for receiving the seismic wave and generating a data signal indicative of the received seismic wave. The seismic acquisition system operates by controlling the placement system with the remote control system to position the buoy and then controlling the operating system with the remote control system to produce a seismic wave from the seismic wave production device. The receivers then receive the seismic wave and generate a data signal indicative of the seismic wave.

Abstract: A sensor arrangement is provided for use in the seismic investigation of geological formations below the seabed. A plurality of sensor nodes (20) are provided and are positioned gfor deployment on the seabed to collect pressure waves and shear waves from the geological formations and to transfer seismic data to a surface receiver. Each sensor node (20) may include a cylindrical structure (22), which is intended to penetrate downwardly into the seabed. At least one, preferably three, geophones (30-32) are positioned in connection with this structure (22). An advantageous method for operating a seismic mapping system with sensor arrangements orderly deployed on the seabed records data concerning system behavior and seismic data. This data may be further processed separately.

Abstract: A method of seismic surveying comprises emitting seismic energy at two or more different depths during a sweep. In one embodiment, the depth of a seismic source is varied during a sweep, by raising or lower the source while it is emitting seismic energy. In another embodiment, an array of two or more marine vibrators is used as the source of seismic energy, with the vibrators in the array being disposed at different depths. The invention allows notch frequencies in the amplitude spectrum to be eliminated, and allows improvements in both the spectral flatness and the amplitude at low frequencies.

Abstract: A non-explosive acoustic source utilizes the combustion of aluminum and water to generate an acoustic pulse. The operation of the non-explosive acoustic source relies on a water/aluminum reaction to generate a burst pressure. The source may be deployed as a single charge or as one element of a multiple charge array and is configurable to explode at variable depths with variable energy levels. The inherent safety of the non-explosive acoustic source obviates the necessity for auxiliary safety features or procedures to protect against inadvertent explosion. As a result, the non-explosive acoustic source facilitates the implementation of sonic detection systems and reduces the operational costs associated with such systems.

Abstract: Disclosed herein is a single point seismic system comprising an array of air guns disposed within a frame. The array includes a cluster of air guns on one of its ends and a reduction in chamber size of the air guns along the length of the array. On the end of the array opposite the cluster the array can comprise a series of air guns whose chamber size is an order of magnitude less than the chamber size of the guns comprising the cluster. The middle of the array can comprise a series of air guns whose respective chamber volumes differ by an order of magnitude. The frame of the present invention is generally wholly submerged during operation and does not interfere with the seismic signal produced by the firing of the air guns.

Abstract: A staggered vertical marine seismic source contains upper and lower arrays (10, 11) of emitters of seismic energy (S11, S12; S21, S22). The upper array (10) is horizontally displaced relative to the lower array (11). The source is used in a marine seismic surveying arrangement that has means for moving the source and at least one seismic receiver. In use, the source is moved through the water in a direction parallel to the direction in which the two arrays are displaced. The arrays (10, 11) are fired sequentially, and the time delay between the firing of the first-fired array and firing of the second-fired array is chosen such that each seismic emitter in one array is fired at the same x- and y-co-ordinates as the corresponding emitter in the other array. The seismic wavefields generated by firing the two arrays are thus generated at the same x- and y-co-ordinates, but at different depths.

Abstract: A method and device for seismic exploration of a subsea geologic formation by pickups set on the sea bottom and intermittently connectable to active data acquisition stations (11) brought nearby. Permanent passive reception stations (1) comprising a heavy pedestal provided with housings for seismic pickups (geophones (6), hydrophone (7) which receive acoustic or seismic signals from the underlying formation are arranged at the bottom of the water body. When collection sessions for the signals received by the pickups are scheduled, mobile active acquisition stations (11) connected to permanent passive reception stations (1) are positioned at the bottom of the water body. The signals picked up are then recorded, for the time required to carry out at least one session of acquisition and recording of the acoustic or seismic signals received by the passive stations in response to the emission of seismic waves by one or more seismic sources.

Abstract: A multi-port projector of acoustic energy in water includes a cylindrical hollow transducer having open annular ends. A thin, flexible member is secured to each annular end to extend across each opening to be displaced by the transducer, and the transducer and flexible members form an interior sealed from ambient water. A battery/electronics module is in the interior and is spaced from the transducer and flexible members to couple driving signals to the transducer for reciprocally displacing it and the flexible members in response to the driving signals. An inert liquid fills the interior around the module, and an open truss on each annular end exposes the flexible members to the ambient water. Cylindrical portions coaxially extending with the transducer on a common longitudinal axis are connected to the open trusses for projecting acoustic energy of lower frequency than conventional cylindrical transducers of similar size.

Abstract: Methods and apparatus for attenuating waves in a bore hole, and seismic surveying systems incorporating the same. In one embodiment, an attenuating device includes a soft compliant bladder coupled to a pressurized gas source. A pressure regulating system reduces the pressure of the gas from the gas source prior to entering the bladder and operates in conjunction with the hydrostatic pressure of the fluid in a bore hole to maintain the pressure of the bladder at a specified pressure relative to the surrounding bore hole pressure. Once the hydrostatic pressure of the bore hole fluid exceeds that of the gas source, bore hole fluid may be admitted into a vessel of the gas source to further compress and displace the gas contained therein. In another embodiment, a water-reactive material may be used to provide gas to the bladder wherein the amount of gas generated by the water-reactive material may depend on the hydrostatic pressure of the bore hole fluid.

Abstract: An underwater sound source which comprises a housing having an inner and an outer surface and a monopole driver suspended within the center of the housing. The housing is adapted to receive fluid therein to form a fluid column inside the housing. The underwater sound source resonates at a frequency of 260 Hz when the monopole driver excites the fluid column.

Abstract: The present invention provides marine vibroseis methods and apparatus that operate in an acquisition time frame significantly shorter than current marine vibroseis acquisition methods and comparable to marine airgun seismic source acquisition, while providing data seismic energy comparable or superior to marine airgun seismic sources, by apportioning a desired vibroseis bandwidth signal over a plurality or multiplicity of vibroseis projectors (sources).

Abstract: A seismic signaling apparatus (100) and method for enhancing the repeatability of the generated seismic signals are disclosed. The seismic signaling apparatus (100) includes a support frame (102) having an air-gun array (114) operably mounted thereto. The air-gun array (114) includes a plurality of air-guns (118, 120, 122) that are positioned such that a tapered, heavy centered, point source seismic signal is generated upon firing of the air-gun array (114). Shock absorbing members (124) are attached to adjacent air-guns (118, 120, 122) in order to absorb the force generated by the firing of the air-gun array (114). In particular, the shock absorbing members (124) absorb the forces associated with air-gun recoil to minimize the movement of the air-guns (118, 120, 122) relative to each other and the support frame (102), thereby stabilizing the air-gun array (114) and enhancing the repeatability of the generated seismic signals.

Abstract: A marine seismic source consists of one or more airguns (1) suspended from a float (2). A supply harness (5) is provided to supply compressed air and electrical control signals to the airguns. The airgun is mounted such that the harness (5) is below the point at which air is emitting from the airgun (1). This means that bubbles of air that rise from the airgun when it is fired do not impact on the harness and so cannot damage the harness.

Abstract: Controlled-polarization marine seismic shear-wave source has a base suitable for positioning on a seafloor, beneath a water body. Twin water-blast tubes (seismic-impulse-generation thrusters) are mounted on the base, aimed upwardly, outwardly in opposite directions at equal acute angles &bgr; relative to the base. These blast tubes are positioned symmetrically on opposite sides of vertical centerline CL of the source. When submerged, water enters open mouths at upper ends of the tubes. The base has multiple downwardly projecting blade-like teeth for penetrating into the seafloor. Firing a compressed-air discharger mounted in a lower end of a water-blast tube hurls a powerful slug of water upwardly along the tube, producing a powerful reaction impulse acting downwardly generally parallel with the tube axis.

Abstract: A seismic shear wave generator comprising a seismic wave source (3) arranged on a base plate (11) arranged for being placed at the seabed, and a coupling device (1) arranged for coupling the wave source (3) mechanically to the seabed in order for shear waves to be transmitted to the seabed. The novelty of the invention is as follows: a cylindrical skirt (1) closely arranged along the base plate's (11) circumference and extending down from the underside of the base plate (11), and open downwards, and a pump device (2) arranged for pumping water respectably out of, and into, the skirt (1) and form vacuum or overpressure, respectively, in a closed cavity formed by the skirt (1) and the base plate (11) and the seabed (1) is lowered onto the seabed. By means of the device mentioned above the shear wave generator may be suctioned fixed to the sea bed and thus transfer shear waves via the skirt (1) to the seabed.

Abstract: A method of detecting a marine gas seep that includes: deploying a local probe on or near the seafloor; producing bubbles in water near or within the local probe; detecting the bubbles; producing data indicating the relative concentration of dissolved gas in the water; and associating elevated dissolved gas concentrations with the presence of a nearby marine gas seep. Another aspect of the invention involves an apparatus configured to carry out the inventive method. Preferred embodiments of the invention utilize an ultrasonic transducer to both produce bubbles and detect them.

Abstract: A sound mitigation system and method reduce the transmission of acoustic output from explosions underwater. The system is submerged to bottom terrain of a body of water and has at a series of gas-generating devices providing volumes of gas that are fed to refractory heat resistant tubing assemblies and flexible general tubing assemblies. The heat resistant and general tubing assemblies extend between adjacent gas generating devices and are provided with at least one row of holes to vent bubbles of gas and form a virtually continuous curtain of bubbles rising to the surface of the water between detonating explosives and areas of interest. The curtain of bubbles mitigates the effects of the explosions on marine mammals and endangered, threatened, or protected species within an area adjacent to the explosions.

Abstract: A reusable low frequency projector system that is capable of producing coherent broadband, high power, low frequency acoustic pressure waves underwater. The projector has two halves each with a spiral wound insulated wire core. The spiral wound wires are separately encapsulated and then joined flexibly in a contiguous parallel orientation. When energized by a voltage source the encapsulated spiral wound wires are repelled from one another and then come back together when not energized, imparting a pressure wave to the water at a desired frequency. The projector requires no pressure compensation devices for operation.

Abstract: A system for detecting source acoustic energy in seismic operations. The system is operable on land and in marine applications. On land, a piezoelectric film is positioned between a vibrator or other source baseplate and the soil. Compression of the piezoelectric film generates an electrical signal proportional to the total ground force, including force due to flexural or resonance of source components, exerted by the seismic source. In marine applications, a source displaces water to produce a pressure pulse in the water, and a piezoelectric film detects the resulting pressure pulse and the flexural movement of the source to produce an electrical signal proportional to the movement of the active component.

Abstract: A sound mitigation system and method reduce the transmission of acoustic output from explosions underwater. The system is submerged to bottom terrain of a body of water and has at a series of gas-generating devices providing volumes of gas that are fed to refractory heat resistant tubing assemblies and flexible general tubing assemblies. The heat resistant and general tubing assemblies extend between adjacent gas generating devices and are provided with at least one row of holes to vent bubbles of gas and form a virtually continuous curtain of bubbles rising to the surface of the water between detonating explosives and areas of interest. The curtain of bubbles mitigates the effects of the explosions on marine mammals and endangered, threatened, or protected species within an area adjacent to the explosions.

Abstract: The invention describes an air gun for use in a marine seismic system. The air gun includes a gun body and shuttle that define a chamber containing a compressed supply of gas. The air gun is further designed to release the compressed gas so that the release time or gun fire time is monitored with sufficient accuracy. The fire time is measured by a timing coil that determines the location of the air gun shuttle by sensing a magnet disposed on the shuttle. The timing coil is designed to eliminate interference caused by magnetic flux generated by the actuation of an air gun solenoid valve.

Abstract: Streamlined, towable, marine seismic energy vibrator for creating intense swept-frequency and pulse-coded seismic signals in a body of water has a sleek, fish-like configuration designed for towing with minimum drag. The vibrator has a streamlined hollow towing head and a streamlined hollow tail head mounted onto front and rear of a long cylindrical tubular wall which is modular, comprising cylinder sections joined in end-to-end axial alignment. Within this long tubular cylinder wall is an axially vibratable multi-piston assembly having a plurality of pistons on a long piston rod. One piston is positioned in each of the cylinder chambers. These chambers hive multiple ports opening out through the long cylindrical wall. An elongated circular cylindrical elastomeric bladder forms a water-filled bladder chamber encircling the wall.

Abstract: A device for canceling non-acoustic self-noise associated with mechanically induced vibrations in sensor arrays and associated methods are described. The method utilizes the isolation of a vibration reference via digital beamforming to non-acoustic wavenumber space. This technique produces an interference reference measurement which is sensitive only to vibrations propagating within an array body and independent of acoustic signals propagating in surrounding medium.

Abstract: The present invention concerns a watertight apparatus capable of being immersed in a liquid, for example a watertight watch, including a case (1) with an inner chamber (10) communicating with the exterior, the chamber being separated from the exterior by a membrane (17) which can be deformed, defining, on one side, a non-watertight outer zone and, on the other side, a watertight inner zone, in which is housed, in association with the membrane, an acoustic transducer (22), the membrane being fixed by its peripheral edge (17A) in the chamber (10) and applied via elastic memeber (20) towards its periphery, but at a distance from the edge, against a support surface (12) arranged in the inner chamber (10).

Abstract: A valving system is disclosed which generally comprises a body including an inlet and an outlet where the inlet is disposed in fluid communication with a fluid flow passage and the outlet is disposed in fluid communication with a pressurized fluid member, the body further defining an internal bore in which is slidably disposed a piston moveable between a first and a second position such that fluid communication between the fluid flow passage and the fluid flow member is established when the piston is disposed in the first position but not in the second position, an apparatus and to move the piston from the first position to the second position so as to interrupt fluid flow from the fluid flow passage to the fluid member.

Abstract: A marine vibrator has a hollow body formed of one shell or of two opposed shells defining an inner space therein with vibrator apparatus within the hollow body. At least one shell has a curved shape, and the shell can have a streamlined shape with relatively low hydrodynamic drag. Certain embodiments include one or more exterior control members to facilitate positioning of the vibrator in water. Other than their mating ends, when two shells are used the two shells may be different in shape and volume or they may be identical. In preferred two-shell embodiments, there is a flexible seal between and connecting the two opposed shells. In certain aspects the inner space is filled with gas. A vibrator apparatus in one aspect applies equal and opposite forces to the shells of a two-shell vibrator or to opposed sides of a single shell vibrator.

Abstract: A method and device for generating a high amplitude sound wave is provided. The device includes a housing having an open end. A piston is slidably disposed in the open end of the housing and forms a chamber for holding a pressurized liquid. The pressurized liquid acts on the piston to move the piston relative to the housing. A latch is operable to fix the piston relative to the housing and to release the piston. Upon release of the latch, the piston moves relative to the housing to generate the sound wave. In the method of the present invention, a piston is fixed relative to a housing to form a chamber between the housing and the piston. The chamber is filled with a pressurized fluid and the piston is released to allow the pressurized fluid move the piston relative to the housing and generate the sound wave.

Abstract: An apparatus for generating acoustic source energy in a liquid medium. A slotted cylinder has an interior volume filled with a fluid. An actuator selectively pressurizes the fluid to expand the slotted cylinder. Movement of the slotted cylinder due to expansion and contraction generates a pressure pulse in the liquid medium to create acoustic source energy. The device provides an acoustic source for marine seismic operations and for use downhole in a borehole.

Abstract: A molded protective body member for seismic cable hydrophone and geophone sensors and their cable splice connections from underwater obstructions and pay-out and retrieval apparatus. The body member is a one piece polymeric member having interior cavities, risers and apertures. When in use, the body member is folded longitudinally in half around the seismic cable at a hydrophone or geophone splice joint and secured in place with recessable molded straps having threaded fasteners passing through each of the body halves thus clamping the body to the cable. At least one interior diametrical cavity is provided consistent with the type seismic cable sensor used. With the sensor and its associated cable and connector positioned within the protective body member, tie wraps are threaded through apertures along and adjacent the longitudinal edges of each half thus closing the interior of the body member. Cavities are also provided internally for placing lead weights.

Abstract: The invention disclosed is a drive assembly for acoustic sources having sound emitting surfaces (1) adapted to be excited into vibrational motions. The invention is especially for use in seismic surveys. The drive assembly includes an electric rotational motor with at least one associated axle comprising at least an axle part (18) and a number of rods (21, 22) arranged radially in relation to the axle. The inner ends of the rods (21, 22) are influenced by the axle part (18) and the outer ends of the rods (21, 22) are adapted to excite the sound emitting surfaces (1) into vibrational motion. The inner ends of the rods (21, 22) are connected to the axle part (18) and the connection is adapted to perform both push and pull forces upon the rods. One or more spring elements (23) are provided between at least one of the rods (21, 22) and the sound emitting surfaces (1).

Abstract: A marine seismic source for generating acoustic source energy. A housing has a continuous exterior perimeter which is moveable to displace water. Movement of the housing can be accomplished by providing alternating convex and concave exterior surfaces connected with inflection points. The composite shape provides movement inwardly or outwardly, and can be moved with different types of actuators. Piezoelectric elements can be activated to move the housing surfaces and to change the internal housing volume. The resulting pressure pulse provides acoustic source energy useful for the evaluation of subterranean geologic formations and for other purposes.

Abstract: There is provided an acoustic source especially for use in seismic studies at sea. The acoustic source has a longitudinal axis and sound emitting surfaces adapted to be put into sound emitting movements towards and away from each other by use of a drive unit. The sound emitting surfaces comprise two curved plate members having upper and lower ends essentially symmetrically positioned in relation to the longitudinal axis of the acoustic source, and forming a convex cross section with their respective upper and lower edges converging towards each other. The upper and lower edges of the sound emitting surfaces, respectively, are connected to each other with two corresponding side elements, the side elements each being connected to at least one hinge stretching along at least a part of the length of the source.

Abstract: Providing encapsulated electronic components on a circuit board by providing dams on a circuit board around areas on which respective electronic components will be mounted, mounting the respective electronic components within the dams on the circuit board, and printing encapsulating material through a stencil in order to provide deposits of encapsulating material over the electronic components and within the dams.

Abstract: A marine seismic cable system for marine surveying comprises an electrical conductor within a tubing for conveying compressed air and electricity between a seismic vessel and equipment such as air guns. The tubing resists elongation caused by water drag forces acting against the tubing exterior surface and provides a protective shield to the enclosed electrical conductor or conductor bundle. This combination uniquely conveys compressed air and electricity while significantly reducing the outside cable diameter to reduce the weight and drag forces acting on the cable system. The combination also permits repair and replacement of the tubing or electrical conductor independent of the other component.

Abstract: Aqueous solutions of N-methylol compounds of carboxamides, urethanes, ureas and aminotriazines or of N-methylol ethers of these compounds that are suitable for finishing cellulose-containing textile materials are prepared by reaction of compounds having one or more N--H groups in aqueous solution with formaldehyde and, in the case of N-methylol ethers, with an alcohol by adding boron trifluoride, a boron trifluoride addition compound or tetrafluoroboric acid or a salt thereof to the aqueous solutions during or immediately after the reaction.

Abstract: An array system, which provides a unipolar acoustic impulse with a broad spectral response underwater, utilizes a vertical array of airgun or electrical spark sources whose individual peak source strengths are essentially constant over the array length, but whose individual source periods vary with depth. The array of sources produces in each instance a near-unipolar, impulsive signature with a broad pedestal-like spectrum. The system may be used for underwater object location and also for seismic exploration.

Abstract: A system for maintaining a spaced relationship between two energetic sources is disclosed, which system including in a preferred embodiment a clamping mechanism securable to the energetic sources, a spacing system disposed between these sources, a pivot mechanism coupled to the spacing system and pivotally engageable to the clamping mechanism, and a shock absorption system coupled to the spacing mechanism and adapted to resiliently deform.

Abstract: A seismic acoustic signal source includes a hull that has a wetted surface in contact with a body of water. When underway, the draft of the hull is substantially zero. An acoustic signal generator is provided with a linear actuator that is resiliently mounted in the hull. The linear actuator is acoustically coupled to the hull bottom such that when the signal generator is activated, the hull radiates an acoustic wavefield into the water.

Abstract: An apparatus and method for modifying the seismic source signal from air guns towed behind a marine seismic vessel. At least one conduit is towed behind the vessel to release bubbles into the water. The bubbles are formed with compressed air released from apertures in the conduit. The size and distribution of the bubbles is controlled by varying the aperture size, the compressed air pressure, the aperture position and orientation on the conduit, and the vessel speed. The bubbles attenuate side directional frequencies to reduce the outwardly directed seismic source signal and to improve the signal to noise ratio at the receivers. By controlling the bubble size and distribution, attenuation of selected frequencies can be controlled.