Abstract: An apparatus for measuring the shear modulus profile of the seafloor by measuring the motion of the seafloor in three dimensions and the wave induced pressure at the seafloor and converting these measurements into a shear modulus profile using the Yamamoto equation and the linear inverse theory of wave-seabed interaction.

Abstract: The present invention enables tomography data in the sea to be collected and transmitted via an artificial satellite to a ground station. Accordingly, data on the Doppler phenomenon and shift of a sound wave is also obtainable based on the temperature and density of sea water and an ocean current. This makes it possible to obtain information about a wide sea area, such as the relationship between the KUROSHIO and the El nino which is now attracting attention in relation to fishery, agriculture and abnormal weather. Hence, the present invention will be of wide application.

Abstract: A ship is provided with booms that may be extended outwardly from the ship. Arrays of geophysical devices of different genera are towed from the booms, in the water behind the ship. A UHF antenna is located on each boom. A line joining the two antennas defines a long reference base line for determining the absolute heading of the ship with respect to a meridian and to locate the absolute positions of selected towed geophysical devices with respect to two-dimensional space. The booms may be oriented along a line perpendicular to the ship's track, independently of the ship's heading for the purpose of maintaining the integrity of the geometric pattern of the arrays of the towed geophysical devices.

Abstract: An apparatus for supplying the power requirements of an Ocean Bottom Seismometer is disclosed wherein the power supply is separate from the power consuming devices of an Ocean Bottom Seismometer and mounted on the weight holding the Ocean Bottom Seismometer on the ocean floor during recording.

Abstract: A pressure wave sensor device is provided including at least two sensitive flexible piezoelectric elements wound in two helices in opposite directions of a tubular support and a method for manufacturing same, said device including a copper conducting ribbon wound helically between the two windings of opposite direction and in the same direction as the underlying winding so as to avoid short circuits at the crossing points of the turns and to improve the electric and mechanical couplings between the two sensitive elements, said tubular support being provided with collector assemblies at regular intervals and wound over the whole of its length with the sensitive elements and the conducting ribbon, the different windings then being cut to the right length at the level of the collector assemblies and connected electrically thereto.

Abstract: A hosewall terminating apparatus for a streamer section utilizing a load bearing flexible hosewall includes an inner sleeve having radially extending outward protrusions and an outer sleeve having radially extending inward protrusions. With the inner sleeve positioned within the outer sleeve, the radial distance between ends of these protrusions are spaced-apart to provide a gap for the position of the flexible hosewall of the streamer section. The hosewall of the streamer section is secured between these protrusions and the sleeve surfaces when the outer sleeve is reduced in diameter by swaging.

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: A ship is provided with booms that may be extended outwardly from the ship. Geophysical devices of different genera are towed from the booms, in the water behind the ship. A UHF antenna is located at the outboard tip of each boom. A line joining the two antennas defines a long reference base line for determining the absolute heading of the ship with respect to a meridian and to locate the absolute positions of selected towed geophysical devices with respect to two-dimensional space. The booms may be automatically oriented along a line perpendicular to the ship's track, independently of the ship's heading.

Abstract: A cartridge retention system includes a cartridge carrying electronic, compressed gas or other components which has a spring-loaded button at one end and which is removably mounted in the breech of an adapter module connected either in a streamer section or between opposing ends of adjacent streamer sections of a towed array. The cartridge is demountably retained within the adapter by providing an adapter housing with a breech which is somewhat longer than the cartridge, and by providing the housing with an overlying two part shell which is rotatable about the housing, with one of the shell parts containing an aperture to accommodate cartridge insertion and with both parts containing an internal circumferential groove adapted to coact with the spring-loaded button on the cartridge to move the cartridge from one end of the breech to the other end upon rotation of the shell.

Abstract: A marine cable for detecting converted shear waves reflected from the strata beneath a body of water in response to a compressional wave generated in the body of water. The cable comprises a jacket, a mount attached to the stress member, a geophone positioned in the mount, a first weight assembly attached to the stress member and positioned proximate a first end of the mount and a second weight assembly positioned proximate a second end of the mount. The mount is sized and made of a material so that its weight is sufficient to cause at least the portion of the cable jacket that is adjacent the mount to contact the seafloor. The first and second weight assemblies are sized and made of material so that their respective weights cause at least the portion of the cable jacket that is adjacent to the respective weight assemblies to contact the seafloor.

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 water vessel of the floating-dock type is provided with an arrangement for adapting the vessel for seismic or similar research. A platform is mounted above the cargo deck and extends between the side walls of the vessel. Research equipment including at least a measurement cable mounted on a reel is supported on the platform. The measurement cable is passed from the reel through the stern door of the vessel into the sea. Cables for transmitting impulses to be measured are situated within spaces provided within the side walls of the vessel so as to be lowerable into the sea from the stern ends of the side walls. According to one embodiment, the platform is mounted so as to be displaceable in the longitudinal direction of the vessel. By means of the invention, a vessel of the floating-dock type can be converted to a vessel suitable for research operations in an economical manner.

Abstract: A method of marine seismic investigation involves positioning or deploying at a predetermined point close to or within a multi-element seismic source array a calibration source which is an acoustic pressure wave point source which has a far-field seismic signature of broad bandwidth. The radiated pressure wave field of the calibration source (3) is weaker than that of the main source (2). The two sources are fired at separate instants within a predetermined time range, preferably with the calibration source (3) being fired about two seconds before the main source (2). The reflected response of the sub-surface strata is recorded and processed to generate seismic data. In one embodiment, the response is recorded with two hydrophone arrays - a short high-resolution array (4) and a conventional main array (5). The method can be used to determine the far-field signature of the main source array (2). It can also be used to obtain a high-resolution shallow seismic section simultaneously with a deep seismic section.

Abstract: An improved ocean bottom seismometer is disclosed wherein a skirted spherical configuration provides bottom weight and provides a sealed area for seawater ballast which may be ejected to provide positive buoyancy for retrieval.

Abstract: An assembly for use in seismic surveys of the sea bed is towed behind a vessel and comprises groups of seismic signal transmitters which are towed through the water, being suspended from float buoys which are combined to form one body which may be formed as a sleeve having limited flexibility. The body is formed with a head member shaped for reducing resistance to the water, and connected to a coupling point for a tow wire to the vessel, which point lies forward of the head member and at the same depth as the transmitters.

Abstract: A technique for a vibration isolation module (VIM) used for towed arrays is disclosed. The VIM has a stretchable cable on which is mounted one or more rigid spacers which make contact with an outer hose formed of a flexible material having a selected vibration attenuation characteristic. The spacer transmits energy between the parts of the VIM which contact the spacer for attenuation purposes. The spacer is "soft mounted" on the stretchable cable so that it may be moved by a limited amount along the cable in response to forces of a specified minimum magnitude. This ability to move allows adjustment of the internal parts of the VIM during use to avoid concentrating stress at any one particular contacting area. Disclosed is an embodiment where two sleeves are used to abut the spacer at opposing ends thereof.

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 broadband matching network for a Helmholtz resonator transducer is a series RL matching network capable of withstanding a high power level. The usable acoustic broadwidth is expanded to produce a symmetrical output over a broad frequency band.

Abstract: A cartridge carrying electronic or other components is removably mounted in the breech of an adaptor module connected either in a streamer section or between opposing ends of adjacent streamer sections of a towed array. The adapter module is provided with channels for loosely guiding all but one strain member, one strain member being clamped to the module, with the longitudinal axis of the module breech being established by the longitudinal axis of the clamped strain member such that alignment of the cartridge is uniquely keyed to the single clamped strain member, the loose mounting of the unclamped strain members preventing differential forces being applied to the adapter module. In one embodiment, a spring-loaded pin and shuttle connector arrangement severs connection for an empty breech and provides for both point contact to an inserted cartridge and relatively long leakage paths so that any entrained sea water will not short out the adapter module or connector system.

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

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

Abstract: A method for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

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

Abstract: In marine seismic exploration, seismic energy is transmitted through a water layer into the earth and seismic reflection signals from subsurface interfaces are recorded. Any undulating water bottom distortion in the recorded reflection signals is removed by replacing the seismic energy velocity in the water layer with a velocity matching that of the earth medium below the water bottom.

Abstract: A system for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continuously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

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: 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 seismic method and apparatus utilizes two point sound sources located at the same location on the earth to produce sound waves at different amplitudes and times. The reflections of the sound waves are analyzed to determine the acoustic properties and rock boundaries within the earth.

Abstract: A marine seismic survey is disclosed in which a plurality of steerage centers are selected for circular traversal thereabout by a marine vessel towing a streamer cable. While the vessel and the streamer are following a circular track about a steerage center, the feathering of the cable creates a separate concentric track line for each of the mid-points between the receivers included in the cable and the source. In this manner an areal coverage is assured which requires no reliance on unpredictable and uncontrollable currents for the desired feathering. An additional important feature of the current disclosure is that there is little wasted time in which the survey vessel moves outside of the overall surveyed area. A preferred course tracking for the vessel is to move from the arc of one steerage course line to another in tangential fashion.

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: In an on-bottom seismometer, the electronic system for operating the release mechanism includes a plurality of independent power sources. A plurality of release condition sensors each produce a release output upon the occurrence of a condition in which the unit is to be recovered at the water's surface. Logic circuitry responds to the release condition sensors for producing a relase signal which is applied to driving circuits for primary and secondary release devices. Switching means automatically connect the logic circuitry and the driving circuitry to an operable one of the power sources.

Abstract: An ocean bottom seismometer unit records refraction waves from a seismic source. The refraction waves are digitzed and stored in a magnetic memory. Periodically, a tape recorder is started and digital samples are transferred from digital memory to tape during a time in which operation of the tape recorder will not generate spurious noise signals which interferes with the detection of the refraction waves. The water break is detected and the time of its occurrence is digitized. Only the digitized time of the water break occurrence is recorded thereby permitting shortened record length and increased record storage capacity.

Abstract: A method of determining source and receiver statics in a marine seismic exploration area overlying a near surface low velocity layer employing a seismic marine energy source, an on-bottom seismic detector cable for measuring seismic reflection signals, and an on-bottom remote seismic monitor for measuring seismic refraction signals.

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: A towing link consists of spaced-apart head and tailpieces. The headpiece includes a towing eye and a pair of lugs for receiving the stress members of a streamer and a lead-in cable. The tailpiece defines a pair of bores through which the stress member and electrical conductors of the two cables are inserted and sealed. A pair of mating connector plugs are provided to interconnect corresponding conductors of the two cables. The assembly is enclosed in a watertight plastic boot.

Abstract: Disclosed is an underwater seismic exploration system utilizing a sonobuoy for the radio telemetry of seismic data signals to a remotely located receiver, the sonobuoy including circuitry for digitizing the analog signals generated by hydrophones suspended from the sonobuoy prior to the application of these signals to an RF antenna. The remotely located receiver includes an antenna for receiving the transmitted modulated digital signal information, and means for demodulating, demultiplexing, and appropriately converting the signals for either analog or digital recording of the received data.

Abstract: A decoupling apparatus for isolating a towed marine streamer from noise transmitted from the tow vessel. The decoupling device comprises a fluid spring positioned in the tow cable with changes in the spring constant being minimized by controlling the fluid pressure.

Abstract: In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

Abstract: In accordance with the present invention, a marine streamer test system and method (MARSTEST) is disclosed for testing field-worthiness of hydrophone sections within the streamer under both passive and dynamic operating conditions. With regard to a passive operating state, five (5) test parameters are automatically generated and compared with upper and lower limits stored within a mini-computer housed aboard the marine exploration boat. Any out-of-specification values trip an alarm network and a printer to warn of the malfunctioning streamer section. Result: replacement or other repair can be effected. With regard to dynamic operating conditions, acceptable "signature" characteristics of the streamer (such characteristics can be 2 or more of the above 5 parameters) are stored within the computer aboard the exploration boat and are compared with actually generated field parameter values acquired during operations, say between "shots", i.e.

Abstract: A hollow, projectile-shaped body containing an acoustical transducer is rased into the sea such that the body descends in free fall until it strikes and penetrates the sea floor, coming to a rest therein. Acoustic signals emanating from the acoustic transducer are processed to generate a direct current analog signal which is a function of the acoustical attenuation of the acoustic signals from a time immediately preceding the body striking the sea floor surface until the body comes to rest in the sea floor, thereby obtaining an indication of the physical characteristics of the sea floor.

Abstract: A marine seismic cable comprising a core; a housing coupled to the core and having a cavity adapted for holding a hydrophone, the cavity being located on a first side of the housing; elastic material positioned in the cavity and extending beyond the boundary of the cavity, a hydrophone positioned in the elastic material in the cavity; and a rigid plate positioned adjacent to the elastic material.