Abstract: A seismic cable (1) and a method of manufacturing such a cable. The cable includes a plurality of elongated electrical/optical elements which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable. A polymeric sheath and a protective outer armoring surround the elements to provide protection against radial stress of said cable. The sensor devices are installed outside of the elements and the armoring.

Abstract: An inner race for a streamer cable connector. The inner race includes first and second curved sections with a screwless fastener for clamping the two sections together about the streamer cable. The two curved sections may be hinged at first ends so that the inner race can be opened like a clam shell for placement about the cable. Cooperating teeth on the second ends of the inner race provide a screwless fastener for the two halves, with the teeth cooperatively arranged to ratchet by each other as the curved sections are closed around the cable.

Abstract: A system for collecting seismic data from geologic formations underlying water. A plurality of hydrodynamic housings are deployable in the water and are permitted to descend at a fast rate through the water until the housings contact the geologic formations. A controller engaged with each housing reconfigures the housing to enhance contact between the housing and the geologic formations and to reduce impact of ocean currents acting against the housing. A marine seismic sensor is engaged with each housing to detect seismic data and to sensor orientation. Each housing can be disconnected from the associated marine seismic sensor to facilitate retrieval of the seismic sensors to the water surface.

Abstract: A conductive rope-like lead-in cable connects a seismic streamer to a towing vessel. The lead-in cable comprises a first electrical conductor at the center core of the cable for carrying a first polarity of power to the streamer for providing tensile strength to the load-in cable. A first layer of insulation surrounds the first electrical conductor. A second electrical conductor for a second polarity of power to the streamer surrounds the first layer of insulation. A second layer of insulation surrounds the second electrical conductor. A layer of seismic data conductors surrounds the second layer of insulation. A third layer of insulation surrounds the layer of seismic data conductors. A metallic protective layer surrounds the third layer of insulation. Steel is effectively and efficiently used both to provide tensile strength and for electrical power conduction.

Abstract: The present invention is directed to a hydrophone streamer towable from a marine vessel on a body of water. The hydrophone streamer comprises a plurality of hydrophones electrically connected in parallel. Each hydrophone further comprises a normally-closed pressure activated switch connected in series with a hydrophone sensor. Each pressure switch is calibrated to open at a predetermined depth in the body of water thereby disabling the associated sensor without affecting operation of other hydrophones in the streamer.

Abstract: An integrated ocean bottom towed four-component array for seismic data acquisition consists of a four-channel electronic section for seismic data collection, a gimbaled three-component geophone and a hydrophone in a housing. The array connects with a submarine cable through a cable joint in order to acquire four components of data consisting of seismic P wave, shear wave and hydrophone in total. Through cable data transmission and processing in a central station, ocean bottom oil and gas structure information can be obtained. Because of the high SNR acquisition in the ocean bottom seismic data acquisition of the present invention, and the waterproof cable interconnections between each of the sections of the present apparatus, data acquisition of high quality can be gained to realize highly efficient and easy ocean bottom towing operations.

Abstract: A marine towed array has a plurality of tow bodies of positive buoyancy each containing a marine acoustic source, such as a vibrator source. Each tow body uses a reel containing an electro-mechanical tow cable connecting the sources, whereby reeling and unreeling of the cable, controlled from a towing ship, changes the spacing of the tow bodies. One of the tow bodies at an end of the array is attachable to the towing ship.

Abstract: A hydrophone array including a cable, such as a towing cable, having attached thereto a plurality of housings. Each housing encloses two acoustic transducers that act as acoustic receivers and acoustic transmitters as requirements dictate during use of the array. The acoustic transducers can comprise piezoelectric transducers, including piezoelectric polymeric transducer materials. Each housing can be hydrodynamically smoothly shaped and have a first bend limiting means extending forwardly from a nose section thereof and a second bend limiting means extending rearwardly from a tail section thereof.

Abstract: Towed low-noise linear acoustic antennas configured for seismic exploration. The jacket of this antenna is pierced with holes that allow seawater to enter the inside of the antenna. The hydrophones are isolated by enclosing them in polyurethane envelopes filled with oil or gel. Buoyancy is ensured by lightening the jacket with hollow inclusions formed from microspheres. Such a structure allows the output noise level of the hydrophones to be reduced by 15 dB.

Abstract: A system and method for generating acoustic source energy in marine seismic operations. A plurality of acoustic energy sources are integrated within seismic streamers to facilitate deployment, power distribution and signal communication. The acoustic energy sources can comprise slotted cylinders activatable with piezoelectric elements. By providing an array of lightweight, energy efficient acoustic energy sources throughout a seismic receiver array, both zero-offset and far-offset reflection data can be recorded. The acoustic energy discharge can be swept over a time interval, or steered in a selected pattern throughout the array, to significantly reduce the impulse energy released into the water. The reflected signals can be compressed back into an impulse for subsequent data processing. Bi-static reflections can be generated simultaneously with the zero-offset source-receiver locations to improve the vertical and horizontal resolution of data.

Abstract: A method for obtaining super source records in a marine application in which a target region is divided into a series of overlapping swaths. Seismic data is then collected for each swath using a fleet of vessels to traverse each swath. The fleet is intended to traverse each swath in a predetermined formation and substantially in unison. Seismic data is collected as each vessel alternates activating its seismic source at predetermined shotpoints along each swath, with reflection data collected by all the receivers after each shot. By careful planning, the proper traversal of numerous overlapping swaths results in a wide array of acquisition data for any given common source position. Super source records are attainable through the processing of this common source position seismic data. These super source records provide wide azimuth seismic data and can be processed to make high-quality seismic images.

Abstract: A seismic cable (1) including a plurality of electrical/optical elements (5) which are arranged to be interconnected with a number of seismic sensor devices (24) arranged at intervals along the cable and installed in a housing (15) integrated in the cable (1). The sensor housing (15) is centrally arranged in the cable (1) and interconnected with a central strength element (2). The electrical/optical elements (5) are arranged over and around the central element (2) and over the housing (15).

Abstract: A system and method for deploying and retrieving streamers behind a tow vessel in a marine seismic array. Each streamer and attached lead-in cable are individually deployed and retrieved into and from the array, and are connected to adjacent lead-in cables with tag lines having a slidable latch mechanism attached to one or more ends of the tag lines. Each latch mechanism is slidable along a lead-in cable until is engages a tether head at a selected location which restricts further movement. Paravanes move the attached array transversely from the centerline of the vessel movement and retain tension on the tag lines. The system uniquely permits retrieval of a single lead-in cable and attached streamer without requiring retrieval of the entire seismic array.

Abstract: A marine seismic surveying method and apparatus are shown. The apparatus includes at least one lead-in which has two or more of the streamers connected to be towed thereby, and which comprises a load-bearing outer sheath to bear the towing forces, an electrical or electro-optical core via which control signals and electrical power are supplied to, and data signals are received from, the steamers being towed by the lead-in, and a connector device series connected in the lead-in, the connector device comprising a body member mechanically coupled between the respective portions of the load-bearing outer sheath of the lead-in on either side thereof, to transmit towing forces therebetween, and a towing attachment for mechanical connection to one of the two or more streamers.

Abstract: A method and apparatus for acquiring high resolution 3D marine seismic data using at least two seismic streamers which are generally parallel to one another longitudinally, and offset from one another in both the vertical and horizontal plane. In one embodiment, the acquisition method uses a vertically staggered source array which is operated using end-fire principles as described below. A processing method is applied for reducing the effect of receiver signal ghosts on the processed signal, thereby allowing the seismic array to be towed deeper without reducing the effective bandwidth of the processed seismic signals. In another embodiment, a vertically staggered source array is utilized. Such that the array provides for the removal of source signal ghosts from the processed seismic and thereby complement the quasi-over under receiver array to synergistically provide for removal of all signal ghosts.

Abstract: Seismic cable for placing on the sea bottom comprising two or more seismic sensor units adapted to detect vibrations in the sea floor and being separated by chosen lengths of cable. The cable is characterize in that the sensor units are substantially heavier per length unit than the cable between them.

Abstract: A seismic streamer comprises a substantially solid core having many of the main components of the streamer, namely hydrophones, electronics modules for digitising the outputs of the hydrophones, the main optical and electrical conductor bundles and Keviar strength members, embedded in it. The core also contains a large number of foam buoyancy elements. An outer skin surrounds the core, defining an annular gap around the core, and this annular gap is filled with open-celled polyurethane foam saturated with kerosene. The capsules containing the hydrophones communicate with the annular gap around the core, so that the kerosene can enter the capsules, each of which contains an open-celled polyurethane foam sheath to cushion the hydrophone. In an alternative construction, made possible by using the buoyancy elements in the core to render the core approximately neutrally buoyant in water, the outer skin and the polyurethane foam are omitted, and the core is used on its own as a solid streamer.

Abstract: A support structure of hydrophones for a towed array sonar system includes elastic members arranged in each sensor package and adapted to support a hydrophone received in the sensor package while attenuating vibrations transmitted to the sensor package. External vibrations, such as vibrations generated due to the running of a towing vessel or vibrations induced due to motions of a towing cable, which are irrespective of acoustic waves reflected by a target moving underwater, are attenuated by the hydrophone support structure during the transmission thereof from the sensor package to the hydrophones, so that the hydrophones are suppressed from vibrating due to the external vibrations. Accordingly, it is possible to reduce noise included in output signals of the hydrophones, thereby achieving an improvement in the sensing performance of the towed array sonar system.

Abstract: A system for underwater seismic prospecting or exploration on seafloors, especially deep seafloors, including streamers designed to contain the measurement devices and to lie on the seafloor, in the form of an inner tube that is non-stretching and non-compressible and an outer tube that is extensible to a certain extent. Through the injection of liquid between these two tubes, the buoyancy of each streamers is made positive. This enables it to be detached from the seafloor and towed to the next measuring position.

Abstract: A multi component seismic sensor which utilises orthogonal accelerometers to determine its orientation. The accelerometers may be used to measure seismic signals directly, or the system may include geophones for this purpose.

Abstract: A cable sectional assembly houses an electrically concatenated series of electronic circuit modules and has electric hook-up media interspersed between the modules. Each run of interspersed hook-up media is surrounded by a flexible tubular member, which is oversized to allow movement of the hook-up media without restriction under flexing of the assembly. The assembly is a construction and arrangement of two forms of moldingly bonded encapsulations. The first of these forms is made of a hard encapsulant and forms a unitary encapsulation local to each electronic module which (i) encapsulates the circuit module and associated electrical coupling connections between the adjacent end of each individual run of an adjacent interspersed run of media and an electrical terminal of the module, and (ii) is securely bonded to the adjacent marginal end portions of the tubular members which surround the adjacent interspersed runs of hook-up media.

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: An encapsulation assembly includes a housing having a nose end, a tail end, and a body portion between the nose end and the tail end. A plurality of acoustic transducers are positioned within the body portion of the housing, each of the plurality of acoustic transducers having a wiring connection attached thereto. A tow cable is connected to the nose end of the housing and is in communication with the wiring connection from each of the plurality of acoustic transducers. A characteristic of the assembly is that at least the body portion of the housing is entirely formed of a solid casting of plastic material thereby environmentally isolating the plurality of acoustic transducers within the body portion of the housing. This configuration prevents water intrusion into the transducer elements, and increases the cavitation threshold for the acoustic array, thereby allowing the array to be driven to higher acoustic intensities.

Abstract: A system and method for deploying and retrieving streamers behind a tow vessel in a marine seismic array. Each streamer and attached lead-in cable are individually deployed and retrieved into and from the array, and are connected to adjacent lead-in cables with tag lines having a slidable latch mechanism attached to one or more ends of the tag lines. Each latch mechanism is slidable along a lead-in cable until is engages a tether head at a selected location which restricts further movement. Paravanes move the attached array transversely from the centerline of the vessel movement and retain tension on the tag lines. The system uniquely permits retrieval of a single lead-in cable and attached streamer without requiring retrieval of the entire seismic array.

Abstract: An apparatus for measuring tensile and bending forces applied to a fat-line towed-array. Tension sensors are configured within a modified fat-line towed-array bulkhead to measure axial tension applied to the front of the fat-line towed-array, while bending sensors mounted further downstream along the fat-line canister interior walls, measure the bending load. The sensor outputs are encoded and digitized before transmitted through a tow line for further data conditioning and processing. The tension and bending sensor data provide information to evaluate the force exerted on the towed-array, allowing a measure of the deployment capability. Measurements taken at various fluid flow rates provide data regarding deployment effectiveness.

Abstract: In a cable with a pneumatic hose, a sheath (9) encloses the hose and conductor elements (6) which are disposed between the sheath (9) and the hose. A layer of compressible material (5) is disposed between the conductor elements (6) and the hose.

Abstract: A seismic cable (1) including a plurality of electrical/optical elements (5) which are arranged to be interconnected with a number of seismic sensor devices (24) arranged at intervals along the cable and installed in a housing (15) integrated in the cable (1). The sensor housing (15) is centrally arranged in the cable (1) and interconnected with a central strength element (2). The electrical/optical elements (5) are arranged over and around the central element (2) and over the housing (15).

Abstract: A seismic cable (1) and a method of manufacturing such a cable. The cable includes a plurality of elongated electrical/optical elements which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable. A polymeric sheath and a protective outer armoring surround the elements to provide protection against radial stress of said cable. The sensor devices are installed outside of the elements and the armoring.

Abstract: A floatation device for marine seismic energy sources. The floatation device includes one or more tubular members and a plurality of couplings for sealing and coupling the tubular members to one another. The couplings include an air valve for filling the tubular members with air. One or more marine seismic energy sources are preferably coupled to and supported by the floatation device.

Abstract: A cable termination for connecting cable armor strands to a cable housing end. Individual wire strands are inserted through apertures in an inner hub and are engaged with the inner hub. An outer hub is connected to the inner hub and the housing for selectively tensioning the wire strands. The outer hub can have apertures for engagement with a second set of wire strands, and can be moved relative to the inner hub to selectively balance the tension in the first and second sets of wire strands. The wire strand ends are connected to the hubs at a selected radial distance from the cable center to strengthen the connection, and different structural combinations between the wire strands and the inner and outer hubs can be constructed.

Abstract: A marine seismic housing having cleats for anchoring geophone sensors to the seafloor, and a method for placing the geophone sensor on the seafloor. The housing is attached to the bottom cable and is lowered into contact with the seafloor. The cleats puncture the seafloor upper surface to improve the coupling between the sensor and the seafloor. The cleats can have different shapes and lengths, and can be integrated within the housing or can be detachable. The housing exterior surface can comprise multiple flat surfaces for enhancing the housing coupling to the seafloor and for increasing the housing stability relative to the seafloor.

Abstract: A method for moving seismic streamers or acoustic energy sources through water in marine geophysical operations. The equipment can be deployed or retrieved from one or more vessels, and two or more tow vehicles maneuver seismic streamers through the water independently of a seismic vessel. Manned or unmanned tow vehicles can tow the streamers ahead of, behind, or to the side of a seismic vessel, or can form an array independent of the seismic vessel. Tow vehicles can be located at both ends to change the tow direction. The invention is particularly useful in customizing an array configuration, in reorienting the array at the end of each survey line, and permits deployment of receivers and sources in different combinations. By decoupling the tow vehicles and streamers from the source vessel, turning time at the survey region borders and the possibility of streamer entanglement is significantly reduced.

Abstract: An acoustic array including a plurality of acoustic sensors positioned at predetermined telemetry points for measuring the acoustic energy from the surrounding environment. The acoustic sensors are each positioned within a fluid-filled pocket in the acoustic array, wherein each the various fluid-filled pockets are separated from each other by a section of solid fill buoyant material. The sections of solid fill material control the buoyancy of the acoustic array. The acoustic array is surrounded by a longitudinally extending outer hosewall which encloses the acoustic array and forms the fluid-filled pockets between the sections of solid fill material. A strength member is extended longitudinally throughout the length of the acoustic array to provide a load bearing mechanism for distributing longitudinal tensile loads applied to the acoustic array, while support spacers are situated within the acoustic array to provide radial support for the acoustic array.

Abstract: A seismic coupling device for geophones firmly couples seismic sensors to the sea floor. The structure is open for the free flow of sea water and mud through the structure so that it moves freely through the sea water and solidly embeds itself in the ocean bottom. It is preferably made of a corrosion resistant metal, such as stainless steel, which also resists bending forces on the cable take-up reel, and provides further mechanical protection for sensor components enclosed within. A segmented ring at each end clamps around the protective enclosure which encloses the sensor package, and a further pair of segmented rings inside the ends clamps around the enclosure. A plurality of axially oriented longitudinal bars couple to the rings to form a squirrel cage around the enclosure.

Abstract: An apparatus for measuring the force applied to a thin-line towed array having a towed array hose formed as part of a thin-line towed array. Coupling components divide the interior of the towed array hose into compartments. Axial tension measurement devices are located within one compartment, and bend measurement devices are located in another compartment. These measurement devices are electrically connected to a digitization and encoding module which is in turn connected to a processing device for providing measurements of the forces on the array.

Abstract: A method is described for the measurement of multidirectional far-field source signatures from seismic surveys whereby a vertical cable acquisition technique is provided, vertical cable data are acquired, the proper receivers are specified to measure the signature, data are sorted into common selected receiver gathers CSRG, the direct wave within common receiver gather is properly windowed, the angles of each direct path are computed and the amplitude of the signatures is normalized, so as to obtain the multidirectional far-field signatures of the seismic source array having the same characteristics as those that generated the seismic reflections.

Abstract: A system and method of processing seismic signals wherein seismic data resulting from a reflected seismic wave is received at a multi-component receiver. A mask trace is generated as a function of the seismic data received at the multi-component receiver, and a single type of seismic signals from the seismic data received at the multi-component receiver is identified and extracted utilizing the mask trace. Generating the mask trace further includes multiplying the seismic data received at two of the components of the multi-component receiver to produce a first result. A positive/negative sign of the first result is identified to produce a first binary result. The first binary result is divided by a scaling factor to produce the mask trace.

Abstract: A propelled cable fairing system for towing objects underwater having a plurality of cable fairings, which are individually propelled by motorized propulsion to avoid the thrust of propellers to overcome normally encountered drag heretofore utilized, which required use of longer and thicker cables resulting in a loss of control over the position of the towed object. In addition, the relative position of the propelled cable fairing system is maintained through a set of serially linked motor controllers that sense the relative position of each propelled cable fairing relative to it adjacent propelled cable fairing. Variation in position of the propelled cable fairing from a target, causes increase in speed of the motor or alters its angle of attack in order to keep the propelled cable fairings in predetermined alignment with the adjacent cable fairing.

Abstract: A system for seismic data acquisition has been invented having, in certain aspects, one or multiple distributed data acquisition subsystems that are independent of energy source controller and/or of navigation system operation. Thus the distributed acquisition system(s) do not require a complicated and burdensome interface to the energy source controller or navigation systems. The seismic data acquisition system supplies a continuous flow of data which is buffered within a centralized data repository for short term storage until required by non-real-time processes. A seismic data acquisition method has been invented that replaces conventional closely coupled interaction between seismic acquisition systems and the energy source controller and the navigation systems by utilizing GPS time stamps on both the data as well as cycling events of the energy source controller and/or navigation systems to insure precise association of seismic data with cycling events.

Abstract: A low friction surface is provided to hose-shaped acoustic envelopes for towed sonar arrays. The low friction surface permits multiple envelopes that are in intimate, parallel contact or that are crossed-over one another, to slide easily relative to one another, enhancing their deployment. The low friction surface is accomplished by blending particles of a low friction material with a base material. The mixture is heat extruded into pellets and the pellets are heat extruded into a hose of desired size. The exterior surface of the resulting hose is then subject to axially aligned abrasion to both expose the particles close to the exterior surface of the hose, and to create axially aligned micro-grooves in this surface. The micro-grooves allow water to enter and lubricate the boundary that is present, which is typically either another hose surface or the metal or other surface of an array deployment vehicle.

Abstract: An arcuate or flat ferroelectric sensor is incorporated in a seismic streamer. The structure comprises an interior cable, a surrounding woven strength member, an overlying foam floatation layer, and an enclosing jacket. One or more elongate channels are formed in the overlying floatation layer, and one or more hydrophones are mounted in the channel(s). The elongate channel enlarges the acoustic aperture for the reception of seismic signals.

Abstract: A non-fluid-filled streamer cable or towed array for performing seismic surveys in water-covered areas includes a plurality of serially coupled active cable sections. Each active cable section includes an electromechanical cable that contains a single central strain member. A wire bundle is placed around the central strain member for transporting electrical power and data through the active section and an inner protective jacket is formed around the central strain member and wire bundle. A foam material is extruded around the inner protective jacket to provide a predetermined buoyancy to the fully assembled active cable section and an outer protective jacket is formed around the foam jacket. A potting compound is formed between, and bonds to, the inner protective jacket and outer protective jacket to provide a water block at each hydrophone location.

Abstract: An underwater cable arrangement comprises an underwater cable capable of being towed through the water, an external device for mounting on the exterior of the cable, and a coil support device disposed inside the cable for supporting a coil. In some embodiments, the coil support device and the external device have engaging portions which co-act with each other to prevent relative rotation of the coil support device and the external device about the longitudinal axis of the cable. In some embodiments, the underwater cable has a skin and the external device is positioned around the coil support device with the skin of the underwater cable between them. The coil support device and the external device have an interference fit with respect to each other to resist relative movement to the coil support device and the external device in the longitudinal direction of the cable.

Abstract: A vertical hydrophone cable includes a support cable, a plurality of hydrophones, and an equal number of delay elements which are tuned to provide synchronization between the seismic and electrical signals. A number of such vertical hydrophone cables are provided. In operation, the vertical array provides a method of seismic exploration comprising the steps of deploying the plurality of vertical hydrophone cables with the integral delay elements, generating a seismic signal, and receiving reflected return signals at the plurality of hydrophones with synchronism between the electrical and sound signals, so that the vertical cable functions in the manner of a traveling wave antenna.

Abstract: A seismic lead-in for a seismic streamer cable has been invented which, in certain aspects, has at least one stress member, the at least one stress member having an interior surface, a first sealing member adjacent the interior surface of the at least one stress member, at least one transmission element positioned within the at least one stress member, the at least one transmission element having an outer surface, a second sealing member adjacent the outer surface of the at least one transmission element, and a fluid in a space, the space defined by and between the first sealing member and the second sealing member. In one aspect the lead-in also includes a housing enclosing one or both ends of the lead-in. In one aspect the lead-in has a port through an end housing extending to the space for introducing fluid into the space and for removing it therefrom.

Abstract: A system and method are disclosed for reducing flow-induced noise in an urwater towed system. The system includes at least one neutrally buoyant towed array, a tow platform for defining a towed direction of the at least one towed array, a neutrally buoyant tow cable connected to the at least one towed array and the tow platform, and a deploy and retrieve apparatus for deploying and retrieving the tow cable. The deploy and retrieve apparatus is connected to both the tow cable and the tow platform. Deployment of the tow cable from the deploy and retrieve apparatus correspondingly deploys the at least one towed array, and retrieval of the tow cable with the deploy and retrieve apparatus correspondingly retrieves the at least one towed array. The speed of deployment of the tow cable can be varied to decrease the velocity of the towed array relative to the surrounding water thus reducing flow-induced noise.

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: Methods and apparatus are described for seismic signal acquisition utilizing an odd number of vibratory sources arranged in line and positioning the sources for one sweep cycle at positions occupied by other sources during the previous sweep cycle. The method has advantages in particular for marine seismic acquisitions.

Abstract: Ocean bottom seismic cables are subject to rolling motions due to seismic wave fields and current action which cause poor receiver ground-coupling and signal distortion, particularly along the cross-line and vertical axes. Two multi-axial receivers are mounted on opposite sides of the cable in a single cluster. When the cable rolls, the axial response of one receiver of the cluster cancels the axial response of the other receiver of that cluster.

Abstract: A marine seismic survey is described which uses measurements made in a mid-field region of the source signature to correct an estimate of the far-field source signature as derived from individual contributions of the seismic source elements. The technique reduces the effects of perturbations which else have a considerable impact on the estimation of the far-field.