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 towable marine seismic source apparatus for producing a high resolution seismic signal at relatively shallow depths for engineering surveys is disclosed. The apparatus support frame operably mounts a plurality of eight identical chambered air guns in a 2.times.4.times.2 configuration to provide a tapered, heavy centered point source. The cylindrical air guns are positioned in a horizontal orientation at a predetermined depth of 1 to 3 meters and are synchronized to fire substantially simultaneously to achieve maximum peak energy output. Two chamber sizes of individual air guns (4 cu. in. & 10 cu. in.) are in a desired range and may be preferably employed in the array configuration to produce the seismic signal having distinct signature characteristics.

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 plurality of sensor arrays are mounted in a streamer cable. The sensors within each array are distributed over an elongated two-dimensional vertical plane. The seismic streamer cable is so constructed that its vertical dimension is substantially greater than its width and the top portion is relatively more buoyant in the water than the bottom portion. Because of that configuration the streamer cable resists vertical strumming and, when the sensor arrays are used in the differential mode, there is no orientation uncertainty.

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: 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 method and device are provided for determining the remote emission signature of a seismic emission array. Interactions make the signatures of the different sources different from those that they have separately. To overcome this difficulty, a catalogue is drawn up of the signatures of the sources actuated separately, as a function of parameters such as the immersion depth for example. Then, during combined use of the sources, the value of the parameters is measured and the signatures are selected from the catalogue which each of the sources would have separately if the parameters had the same values as those which are measured. The overall remote signature of the device is obtained by combining the selected signatures.

Abstract: A wide-range audio frequency underwater transducer is designed to make use of a massive small diameter vibratile piston driven by electromagnetic oscillatory forces to transmit omnidirectional uniform sound pressure level over the frequency range 100 Hz to 5 kHz. The rugged transducer design is adapted for low-cost mass production and can be used as a highly reliable expendable reference standard of source level for the calibration of in-situ stationary or moving sonar receiving systems. The magnitude of the source level can be accurately controlled by the magnitude of the electrical current supplied to the electrical winding over the entire frequency range of operation. A pressure equalization system is included in the design that permits use of the transducer at any depth down to 500 feet.

Abstract: The aft drogue module (18) of the towed sonar array has a body (20) as its main length. The body (20) contains strength member (26) which is covered by an extruded tube (28) of rubberlike material which is covered by braid (30) and which, in turn, is covered by extruded abrasion-resistant cover sleeve (32). At its forward end, the strength member is expanded into the conical interior of coupling (22). The tail (56) is attached to the body and contains fill material (60) which damps and is sufficiently stiff to inhibit whipping during towing.

Abstract: An active, low-profile hydrophone for use in aquatic environments having substantially turbulent flow conditions. The hydrophone is generally pisciform such that it may lie substantially flat on the water bottom and oriented in the current so as to reduce ambient noise associated with the turbulent flow. The enclosed sensors are oriented such that they are insensitive to acceleration and are coupled to a unity gain amplifier network also contained within the hydrophone.

Abstract: A high ambient liquid pressure-resistant electrical connector is shown with an airgun having a solenoid actuated valve mounted on the airgun. A multi-conductor electrical cable is connected by this pressure-resistant connector to a plurality of terminals of the solenoid valve for protecting from ambient liquid the terminals and the adjacent portions of the conductors. This pressure-resistant electrical connector includes a connector housing having an upper end and a lower end, with the lower end of the housing being mounted to the airgun. The connector housing has a fluid sealant chamber for enclosing the electrical terminals and adjacent portions of the conductors connected to the terminals and includes at least one barrier for engaging the cable to protect against ambient liquid seeping past the barrier to the electrical terminals. The connector housing defines a cylindrical space carrying a spring-loaded piston.

Abstract: Disclosed is an underwater seismic energy source which includes a plurality of airguns. Each of the airguns has substantially the same size, weight and external configuration, but the internal capacities are configured such that when the guns are fired the primary pulses interfere constructively and the bubble pulses interfere destructively. Each of the airguns is connected in the same way to an individual tow line, each having the same length. When the airguns are towed, they are maintain substantially the same depth, even without flotation devices such as Norwegian buoys or rigid floats.

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 dual chamber seismic air gun which discharges both chambers simultaneously to counterbalance the reactive forces generated by the discharges. The chambers are symmetrical within the housing of the gun so that the movement of the internal parts during operation also counterbalance each other. The gun is mounted coaxially on the air supply of a seismic array to provide a good profile for towing.

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

Abstract: A device for use in borehole-seismic measurements at sea whereby seismic energy sources (7) are suspended below the surface (D) and connected to a handling line (2) which is operated by a crane arrangement on a vessel. By suspension of a minimum of two seismic energy sources (7) from a stand (3) at a distance from mutually separated floats (1) rotatably connected on horizontal axes (9) to the stand, seismic energy sources (7) can be placed and maintained at a constant depth below the surface, whereby several seismic sources (7) can be used simultaneously. The stand (3) is equipped in its central area with a guide (4) for the handling line (2), which is divided at the end connected to the respective energy sources' (7) suspension lines (8), which simplifies the positioning of the device.

Abstract: The far-field pressure signature of an air-gun array is derived from near-field measurements. An array of air guns is deployed in the water at a desired depth. A hydrophone is suspended in the middle of the array at the same depth so that the guns are equidistant from the hydrophone. The lateral spacing between the guns and the sensor is much less than the water depth of the guns. Having fired the guns, the ghost reflection amplitude in the near field will be much less than the amplitude of the direct arrivals and can be ignored. The far-field signature is determined by inverting the observed pressure signature, delaying it in proportion to array depth and adding the inverted, delayed signature back to the original signature.

Abstract: The invention is a multi-port, multi-chamber, tuned, air-powered subsea seismic source. It is suitable for producing a seismic wave in a subsea environment during seismic prospecting. Interconnected pressurized chambers are formed between plates located on a movable shuttle and cylinder walls extending inward from the source housing. The source is fired by moving the shuttle through a stroke and allowing the pressurized air within the air chambers to exit through ports into the surrounding water. A unique seal arrangement in also shown.

Abstract: A method for obtaining far-field signatures of marine source arrays by the downward continuation of near-field data recorded along a short signature streamer of closely spaced hydrophones, located beneath the array. This method has several advantages over conventional far-field signature measurement techniques. The technique can be used in water depths as shallow as 50 meters, it does not require any precise knowledge of the array geometry or of the location of the recording sensors, and it may be used on a shot-by-shot basis to obtain signatures for use in a shot-by-shot signature deconvolution.

Abstract: A method for determining the effective or apparent firing time of a seismic source. The seismic detectors positioned at known distances from the source, but outside the non-linear acoustic region, are used to detect arrivals of energy from the source. The arrival times and known distances are used to determine effective source firing time which is in turn used to calibrate the source for actual seismic operations.

Abstract: A seismic source drives one or more jets of high velocity water into an underwater environment and then terminates the jets by means of a valve member, the motion of which is controlled to obtain precisely timed high energy seismic pulses to provide reflected signals from which high resolution seismograms may be obtained when the signals are processed.

Abstract: An improved method and apparatus for gathering seismic data in a region covered by a body of water. Gas bubbles are formed in a zone of water adjacent a streamer containing hydrophones to form an acoustic lens for refracting acoustic waves which have reflected from the sea floor or subfloor geologic structures. This zone reduces the amount of noise at the hydrophones due to multiple reflections of sound between the water surface and floor. In the preferred embodiment, a pair of perforated gas dispensing tubes are towed from a seismic vessel. The tubes are maintained in a fixed position relative to the streamer generally above and on opposite sides of the streamer by a pair of paravanes, one attached to each tube. A gas compressing means aboard the vessel supplies gas to the tubes. The gas then escapes through the perforations in the tubes to form the zone.

Abstract: The disclosed device is a marine seismic source which produces a varying FM signal often in the 10-100 Hertz region of the spectrum. The seismic source uses stiff oscillating radiators to create a signal in the water. These radiators are actuated by hydraulic cylinders which are in hydraulic communication with hydraulic or oleo-pneumatic variable devices acting as springs with a variable spring rate. Variation of the spring rate as a function of the frequency permits the device to be tuned for maximum power output.

Abstract: The invention provides an improved method and apparatus (10) for measuring the velocity and amplitude of sound waves (150) from acoustic pulses (145) generated near the mudline (130) of the seafloor (120). The apparatus (10) includes a seismic source (30) for generating the acoustic pulses, one or a plurality of vertically spaced sensors (50) located vertically below the seismic source (30) for sensing when the sound waves (150) impact the sensors (50), a hydrophone sensor (200) located on the vessel (60) for measuring the distance to the seismic source (30) a crane and winch for pulling the embedded sensors (50) upwardly and out from the sediments, and means (100) for firing the seismic source when said sensors (50) are being pulled upwardly, for taking amplitude and velocity measurements from each sensor, and for determining the distance the sensors have been pulled upwardly for each acoustical pulse operation.

Abstract: An armored umbilical and termination housing is disclosed for towing a sub-array of seismic air guns used in marine seismic surveying comprising a single air hose for supplying all the high pressure air to the individual air guns surrounded by all the electrical control cables needed to operate the air guns in the sub-array. Protective coatings are applied around the electrical control cables and stress members for carrying the laod of towing the sub-array are incorporated within the umbilical. A termination housing is provided on the end of the umbilical for terminating the single air hose and all the electrical control lines to common connectors so that individual electrical control lines and air hoses can run from the termination housing to each individual air gun in the sub-array. Air shut off valves are provided so that the high pressure air can be shut off to the individual air guns within the sub-array remotely from the survey vessel.

Abstract: The invention provides a system having at least one subocean bottom seismic device, such as a seismic source (10) or a seismic detector (600), and a planting unit (300). When the planting unit (300) is lowered it selectively implants the seismic device at predetermined locations in the ocean bottom, it releases from the implanted seismic device, and, when raised, uncoils a signal cable (30) from the implanted seismic device. The signal cable (30) which is capable of retrieving the implanted seismic device (10, 600) is connected to an anchored buoy (40) which contains a first communications unit (70). A second seismic device (100) is carried in a predetermined pattern near the implanted seismic device and is connected to a second communication unit (130).

Abstract: A gun shot control unit for a seismic exploration system compensates for the inherent delay between the shot command signal and the actual occurrence of the seismic pulse. A digital clock is synchronized with an external source. Timing pulses occurring at a time preceding the timing pulse upon which the occurrence of a seismic pulse is desired are produced by the clock. These timing pulses start a digital counter at a time preceding the desired time of occurrence of the seismic pulse. This counter is adjustable so that the delay which interposes between the timing and the actual occurrence of the seismic pulse can be minimized.

Abstract: The present invention relates to a method for initiating an underwater implosive seismic source which comprises the steps of: measuring the instantaneous pressure at the location of the source; determining, from this measured pressure, the bubble period separating the firing signal from the implosion peak of the shock wave; and initiating the source with a delay or advance of a value equal to the difference between the bubble period corresponding to the instantaneous pressure and that corresponding to the mean pressure. The invention also provides a device for carrying out this method which device comprises; means for measuring the instantaneous pressure in the neighborhood of the source; comparator means (C5) for comparing this pressure with a mean value; and time delay means (C3, C4) for delaying a firing signal (S1) by a value which is a function of the result of this comparison.

Abstract: An offshore drilling tower has at least one upright hollow member extending from below the water to support an above-water platform. A detector in or on the hollow member, usually below the water, responds to a water leak into the hollow member. The detector includes a signal generator responsive to pressure or chemical effect of the water. The detector is effective when actuated by water intrusion into the hollow member and into contact with the detector to send a signal of a unique or distinct frequency through the member itself to a signal receiver, preferably on the platform. The receiver is tuned to the distinct frequency and is effective upon receipt of such signal to afford an indication that the detector has been actuated by a water leak at a particular location.

Abstract: A method for marine seismic exploration, comprising the steps of first discharging simultaneously a set number of seismic sources having a known volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection by a same series of reflection points are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.1. The sum signal is subsequently filtered by means of a suitable filter operation having a frequency range f.sub.1, resulting in a sum signal having substantially equal phase of the individual components in the frequency range f.sub.1, next discharging simultaneously a set number of seismic sources having a known volume V.sub.2, different from volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.2.

Abstract: A marine seismic streamer cable having both pressure responsive and acceleration responsive transducers disposed therein. The accelerometer responds to acceleration along one axis regardless of its orientation about the other axis. The accelerometer is mounted in the streamer cable and responds to accelerations produced by a seismic source but is insulated from the noise and motion produced as the streamer cable is towed through the water.

Abstract: In order to determine the signature of an array of n seismic sources 21 to 27, for instance marine seismic sources in the form of air guns, the array is actuated and the emitted pressure wave is measured at n independent points whose positions will respect to the array are known by hydrophones 31 to 37. The measurements are processed to produce n equivalent signatures of the n sources taking into account the interactions therebetween. The signature of the array is then determined merely by superposing the n equivalent signatures.

Abstract: An apparatus is provided wherein one air supply is used to supply compressed air for a plurality of multi-size seismic pulse generators.

Abstract: A seismic data acquisition system for use in shallow water covered areas comprises a flotation device which serves also to house the electronic components; anchoring device with mechanical filter device to protect the anchor, so as to insure its maintaining its position; seismic sensor device for detecting seismic waves in the water and converting them to electrical signals; radio receiver device for receiving operational control instructions; and device for amplifying, digitizing and storing the electrical signals provided by the sensor, preferably on a removable tape recording device.

Abstract: The invention provides an apparatus (10) and method for measuring the velocity and amplitude of a pressure wave (310) from an acoustic pulse (300) through layers of sediment (140) located below the mudline (130) of the seafloor (120). The apparatus (10) includes an implosive seismic source (30) for injecting acoustic pulses (300) into a region of the sediments (140), a plurality of vertically spaced sensors (50) located vertically below the seismic source (30) for sensing when the pressure waves (130) from the acoustic pulses (300) impact the sensor (50) or the amplitude of the pressure wave (310), and a digital recording system (100) for recording the signals from the sensors (50).

Abstract: The invention relates to a marine seismic source which emits an FM signal linearly increasing from 10 Hz to about 100 Hz. The source has a number of transducers which are flexible sleeves containing a pulsing hydraulic fluid.

Abstract: Seismic exploration method in arctic regions involving the generation of a seismic disturbance in the water beneath the ice in areas where conventional marine and land exploration methods are functionally inadequate. Seismic disturbances are generated by an air gun assembly which automatically executes lowering air guns through apertures in the ice and retrieving them while carrying out preventive measures against freeze-ups. Seismic sensing and recording equipment are positioned within an appropriate range to detect seismic data in the form of reflective or diffractive signals generated in response to the seismic disturbance after actuating the air gun array, wherein the seismic data is indicative of sub-surface structural formations existing below the body of water.

Abstract: Disclosed herein are improvements in a recoil reducing system of a gas gun which create pulses in a liquid medium by introducing therein gas under high pressure. The release of high pressure gas from the barrel of such a gas gun causes recoil of the barrel. To reduce recoil, a reaction plate is attached to the barrel by metal rods so that the high pressure gas will impinge upon the reaction plate before escaping into the medium, and the force exerted on the reaction plate by the impinging gas will at least partially balance the force of recoil. In a preferred embodiment of this invention, a layer of shock absorbent material is interposed between the reaction plate and the impinging gas to absorb some of the energy of the gas. Flexing of the metal rods is thereby reduced and the life of the rods is extended. Alternatively, the flexing of the rods is reduced by connecting each rod to the reaction plate through a chain link type of connection comprising two rings, each ring passing through the other ring.

Abstract: A heave compensation system for an underwater towed seismic system of the kind in which a body containing a sound source and hydrophones is towed behind a ship, and a recording is made of echoes from the bottom and sub-bottom layers. An accelerometer in the towed body produces a signal indicative of the vertical acceleration of the body. The acceleration signal is double integrated within a frequency range having a low frequency roll-off to produce a position signal which is used to adjust the firing time of the source. If the fish heaves upwardly, the firing time is advanced; if the movement is downwards, the firing time is delayed. Preferably a pressure transducer in the fish produces a pressure signal which is also used to adjust the source firing time, for pressure variations below the lowest likely wave frequency. The crossover of the pressure and acceleration compensation systems is typically about 0.01 Hz.

Abstract: A marine seismic streamer to be tested is towed through the water in a fully deployed state past a lightweight, portable acoustic energy source submerged beneath a stationary float. The electrical output of multiple pressure transducers distributed along the streamer is recorded on the towing vessel in response to acoustic pulses generated every few seconds by the source, a separate channel being indicative of the combined transducer output of each streamer section. Output signals failing to exhibit normal wave shape or decay characteristics as the distance varies between individual streamer sections and the stationary source may be indicative of faulty transducers or electrical or mechanical cable failures.

Abstract: In marine seismic exploration, seismograms recording reflected energy generated from the firing of a seismic source are used to measure the characteristics of the medium through which the energy passes. These measurements are converted into control parameters for an array of seismic sources. When the array is fired under control of these parameters, seismograms having enhanced reflections are produced. As an example, at least one seismic source is fired to produce seismograms which are used in the measurement of water bottom reflectivity and water depth. The measured reflectivity and water depth are converted into a time domain operator representative of the inverse of the reverberation distortion in the water layer. An array of sources is then fired in a sequence which produces an acoustic pressure wave having the inverse time domain characteristics.

Abstract: A marine gun for the production and timing of underwater pulses by the discharge of gas under pressure comprises a body having at least one port, means retaining the gas in said body under pressure and for allowing it to discharge through said port to produce said pulses, said gun including at least two electrodes which make electrical contact with the water in the path of gas discharged through said port such that such a discharge of gas increases the electrical resistance between said electrodes to produce a timing signal.

Abstract: Seismic exploration method in arctic regions involving the generation of a seismic disturbance in the water beneath the ice in areas where conventional marine and land exploration methods are functionally inadequate. Seismic disturbances are generated by an air gun assembly which automatically executes lowering air guns through apertures in the ice and retrieving them while carrying out preventive measures against freeze-ups. Seismic sensing and recording equipment are positioned within an appropriate range to detect seismic data in the form of reflective or diffractive signals generated in response to the seismic disturbance after actuating the air gun array, wherein the seismic data is indicative of sub-surface structural formations existing below the body of water.

Abstract: A seismograph pickup for use at the bottom of the sea, comprises a detector, a frame, detachable ballast, and a sealed and water-tight container mounted on the frame. The container floats for bringing the pickup to the surface when the ballast is detached. The detector is outside the container so that it may be deposited on the sea bed. The detector is connected to the container by means of an electric transmission cable and a mooring cable. The container includes a power source and means for recording signals delivered by the detector. The invention is also concerned with means for supporting the detector on the frame and for unhooking it when the detector is released.

Abstract: A heave compensation system for an underwater towed seismic system of the kind in which a body containing a sound source and hydrophones is towed behind a ship, and a recording is made of echoes from the bottom and sub-bottom layers. An accelerometer in the towed body produces a signal indicative of the vertical acceleration of the body. The acceleration signal is double integrated within a frequency range having a low frequency roll-off to produce a position signal which is used to adjust the firing time of the source. If the fish heaves upwardly, the firing time is advanced; if the movement is downwards, the firing time is delayed. Preferably a pressure transducer in the fish produces a pressure signal which is also used to adjust the source firing time, for pressure variations below the lowest likely wave frequency. The crossover of the pressure and acceleration compensation systems is typically about 0.01 Hz.

Abstract: A system for marine seismic exploration has arrays of sources and receivers which discriminate against horizontal traveling source-generated noise. Directive arrays of sources or receivers have a length which is longer than the wavelength of the lowest frequency of the seismic pulse. The spacing between the elements in the array is less than the wavelength of the highest characteristic frequency in the seismic pulse.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. The synchronization and timing is achieved by controlling and monitoring the movement of the shuttle in the air gun. Various sensors are used such as an electrical coil having a constant current flowing therein which produces a flux pattern which is modified when the shuttle is accelerated, thereby inducing a voltage in said coil which is processed by appropriate processing circuitry. Another embodiment employs a magnetic sensor which includes a permanent magnet and coil wrapped therearound; the permanent magnet produces a flux pattern which is altered when the shuttle is accelerated and comes into proximity to the sensing end of said permanent magnet, thereby inducing a voltage in the coil which is then processed in appropriate processing circuitry.

Abstract: A geophone assembly for use in a marine seismic cable to detect converted shear waves reflected from the strata in response to a compressional wave generated in the body of water associated with the strata. The geophone assembly comprises a cylindrical mount that has a central aperture and a geophone positioned in the central aperture. The mount has a plurality of additional apertures that are sized and positioned to accommodate the plurality of stress members in the cable, and the mount is sized and made of a material so that the weight of the mount is sufficient to cause at least the portion of the cable jacket that is adjacent the mount to contact the seafloor.

Abstract: A method for controlling the firing times of a plurality of marine seismic sources which are towed as a seismic array behind a towing vessel is provided. The marine seismic sources are adapted to create seismic pulses after having been fired. The method measures and determines physical quantities representing the instantaneous operating depths of the individual seismic sources of the array and transmits the values of said quantities to a controling means for the seismic sources which compares the depth values thus obtained with predetermined depth values, and, if the measured depths are different from a preset depth, adjusts the firing times of the seismic sources of the seismic array in relation to the measured instantaneous depth values.Apparatus for carrying out the method is also provided.