Abstract: In a multichannel seismic system, channel-sequential seismic data samples gathered during a first recording cycle are demultiplexed to sample-sequential format in a core memory. The core memory is divided into pages each of which is addressable in two dimensions by rows and columns as a rectangular matrix. The channel-sequential data samples are serially loaded into the respective pages in channel-sequential order by columns. At the end of the first recording cycle, the data are extracted from the respective pages by rows in sample-sequential order. As the data samples from the first recording cycle are being extracted by rows, data samples from a second recording cycle are loaded serially by rows into the respective pages that were vacated by the extracted data samples of the first recording cycle.

Abstract: An improved air gun consists of an elongated cylindrical housing for containing a volume of compressed air that is closed at each end by end plates. A radially-positioned exhaust port is bored into the wall of the housing. A hollow, cylindrical shuttle, is mounted concentrically inside the housing for linear back-and-forth sliding motion in alternate strokes. The ends of the shuttle are closed by end faces. A radially positioned sealing pad has an orifice that is alignable with the exhaust port is supported by the shuttle. When the shuttle is at either end of a stroke, the sealing pad blocks the exhaust port. The space between each shuttle end face and the respective housing end plates form shuttle-actuation control chambers. A small air leak in each control chamber maintains the residual air pressure therein at ambient when the guns is inactive. To fire the gun, a small quantity of air is diverted by valving from inside the housing to one of the control chambers.

Abstract: In the field of seismic exploration, compressed-air guns may be used as sound sources. Known air guns employed complex valving and were wasteful of compressed air. The air gun sound source of this invention is of simple construction and is economical of compressed air.The gun (10) consists of an elongated housing (34) that has at least one radially-positioned exhaust port. The housing is charged with a volume of compressed air. A hollow cylindrical actuator (60) is mounted inside the housing and may be hydraulically or pneumatically driven within the housing in longitudinal strokes. The actuator has at least one radially positioned aperture (88) alignable with the exhaust port. A valve or sealing pad (96) is mounted in each aperture. An orifice (104) is cut into each pad. At one end of an actuator stroke, the valve blocks the exhaust port in the housing.

Abstract: A marine seismic streamer-cable section includes a plastic tubular jacket reinforced by tough, braided-fiber tapes embedded in the jacket wall. A termination fixture is fastened to each end of the cable section. The termination fixture includes a bulkhead, an untapered end of which fits snugly into the plastic jacket. The other end of the bulkhead is tapered and protrudes from the end of the jacket. Short lengths of the reinforcing tapes are exposed by stripping away some of the jacket wall. A cylindrical wedge grips the exposed tapes between the inner wall of the wedge and the tapered portion of the bulkhead. The tapes are doubled back over the outside of the wedge and are bound to the jacket and to the untapered end of the bulkhead by bands.

Abstract: In seismic exploration, particularly at sea, several seismic acoustic sources selected from different genera of such sources are combined in a single array. The several sources are fired substantially simultaneously so that the acoustic pulses from the several sources blend together to create a single composite seismic wave. The source genera are selected such that their initial impulses are in phase but their caudal transients are incoherent with respect to one another so that the initial impulse is enhanced at the expense of the after-pulses.

Abstract: The electric multi-contact connector consists of twin half-housings. Each half-housing carries a plurality of contact holders independently mounted in spaced-apart relationship on a multi-bore base. The prong-end of each contact is resiliently supported by its holder and makes a water-tight joint therewith. When the two half-housings are moved into latching engagement, each pair of mating prong-ends of the opposite connector half-housings inosculate. Each prong-end is preferably serrated to improve the conductivity between each mating pair of prong-ends under adverse operating conditions.

Abstract: Seismic waves are detected for a given seismic prospect with an accelerometer and a hydrophone and the outputs of said accelerometer and hydrophone are combined directly to create a signal for seismic analysis. The accelerometer and hydrophone may be combined physically in a single composite unit for recording the seismic waves or an accelerometer and hydrophone may record the seismic survey independently for subsequent combining of the signals from the accelerometer and hydrophone.

Abstract: A conventional electromagnetic geophone includes a coil assembly that is spring-suspended in an air gap between concentric pole pieces of a magnet. The coil assembly is wound on the outer wall of a bobbin. The bobbin is typically made from or includes a metallic material to provide a mass for mechanical damping and a conductor for electrical eddy-current damping of the spring-suspended coil assembly. The improvement of this invention lies in mounting on the bobbin, a vernier mechanical damping mass made of a coil of insulated wire. The coil is open-ended and the mechanical damping force is adjustable in accordance with the number of turns in the coil.

Abstract: A survey ship proceeds along a desired track as determined by precision navigational aids. A doppler sonar is programmed to receive returns from various water masses circulating at various depths between the ship and the water bottom. The doppler sonar scans the different depths by changing the signal return-time window. The ship's track resolved with the water-current velocity components to obtain a resolved water current vector. The doppler sonar may be an integral part of the navigation system. In such a case, the doppler sonar will be commanded to lock on the water bottom at selected intervals to determine the true ship's track and at other intervals, the sonar will track one or more water masses. Alternatively, two sonar signal receivers may be used, one to continuously track the water bottom and one to scan the water masses at various depths.

Abstract: The seismic transducer comprises a hollow, elongated casing having a bore defining a chamber. An opening extends through the wall of the casing into the chamber. A hydrophone is removably disposed inside the chamber. The hydrophone comprises an elastomer body in a portion of which is embedded a rigid cage marginally supporting a pressure detector assembly. Means are coupled to the casing for exerting a static pressure on the elastomer body. The cage has a geometric configuration adapted to substantially shield the detector from the static pressure which causes the end portions of the elastomer body to expand outwardly, whereby each end portion forms a fluid-tight seal against the wall of the chamber.

Abstract: The underwater charge launcher linearly ejects a small, water-propelled explosive charge into the water from the open end of an ejection barrel trailed in the water behind a seismic exploration vessel. The charge is detonated, after a one to two-second delay, when a percussion-ignitable delay cap in the end of the charge impacts a firing member positioned adjacent the open end of the ejection barrel. The firing member includes a firing pin mounted on a rotatable, spring-biased striker plate having a U-shaped rim. When a charge is ejected from the barrel, the primer cap impacts the firing pin. The kinetic force of the ejected charge acting against the firing pin overcomes the moment of inertia of the striker plate, causing it to rotate the firing pin out of the path of the charge. The charge is supported and guided by the unobstructed portion of the U-shaped rim of the striker, as the charge is ejected out of the launcher. After a preset delay, the charge detonates when it is a safe distance from the launcher.

Abstract: An improved base plate for a vibratory seismic signal generator consists of a plurality of parallel T-bars welded together. The flange of every adjacent T-bar is inverted with respect to its neighbors.

Abstract: The marine connector comprises a pair of complementary connector units, each attachable to an electric cable-end for interconnecting the same. Each connector unit has longitudinally-spaced, front and rear end walls interconnected by an axial transverse partition. Male and female electric contact elements are mounted on the front wall of each connector unit on opposite sides of the partition and are aligned for telescopic connection with one another. The conductor ends are anchored to the partition by means including a solder ball and extend therefrom to the related contact elements. A sealing sleeve made of a flexible resilient material is slidably mounted on the cable-end portion leading to each unit.

Abstract: An air actuated seismic signal generator, commonly termed an air gun includes a cylindrical casing that is divided into a control chamber and a firing chamber by a sliding valve. The end face of the sliding valve that is exposed to the control chamber has a greater area than the end face exposed to the firing chamber. An air exhaust port is provided in the firing chamber; the exhaust port may be opened or closed by sliding the valve away from or towards a seat that is associated with the exhaust port. Air is admitted to the control chamber at a relatively low pressure of about 500 psi, and holds the valve in the exhaust-port-closed position because of the differential forces on the valve end faces. The firing chamber is pressurized to a relatively high pressure of about 5000 psi by a separate air supply. There is no air communication or equalization between control and firing chambers.

Abstract: A rapid-fire air gun for generating acoustic pulses in a body of water includes a reservoir of high-pressure air, a shut-off valve, and a throttle valve for admitting air to an attached firing chamber. The firing chamber has an exhaust port that is sealed by a spring-loaded exhaust valve. When the shutoff valve is open, high pressure air is admitted to the firing chamber through the throttle valve at a rate depending upon the effective aperture through the throttle valve. The exhaust valve is set to open at some selected pressure and to close at some lower pressure. When the air pressure in the firing chamber exceeds the pressure setting of the exhaust valve, the valve opens to impulsively release a jet of high pressure air which generates an acoustic pulse. When the air pressure in the firing chamber drops, the valve closes and the air pressure again builds up in the firing chamber. A series of such openings and closings generates a pulse train.

Abstract: The transducer unit includes a rigid hollow casing. The casing defines through its cylindrical wall a plurality of sound-transmitting windows. A hydrophone having an elastomer core is removably positioned in the bore of the casing opposite to the windows. A pressure transducer element is embedded inside the core. The core is slightly compressed so as to form plugs for the windows.

Abstract: The seismic system includes a seismic sensor cable assembly having 50 cable sections and much of the seismic data processing electronics decentralized into the cable structure itself. The cable assembly is coupled to a central station mounted in a recording vehicle. The central station includes recording circuitry and apparatus to receive, process and record digital data words from a data link in the cable assembly and circuitry for transmitting control signals into an interrogation link in the cable assembly. The electrical output of each sensor unit constitutes a separate input channel. The cable sections are spaced apart and interconnected by small-diameter, cylindrical connector modules which contain a transceiver unit for processing the signals from ten sensor units in an associated cable section. Contained within each transceiver unit is a multiplexer having a plurality of filtered input channels coupled respectively to the elemental sensor units, and an output.

Abstract: Sets of at least three geophones are oriented in different directions perpendicular to the longitudinal axis of a seismic cable in which they are assembled, so that at least one geophone in each set will detect substantially vertically-propagating reflected seismic signals when the cable is rotated in any orientation about its longitudinal axis. Arrangements may be provided to selectively enable the one geophone of each set that has its axis most nearly oriented to the vertical.

Abstract: It is a purpose of this invention to dispose a large number, such as 500, of elemental seismic sensor units over the earth's surface in a desired pattern. The sensors are arranged preferably in a linear pattern, at increasing distances, remotely with respect to a central station. Each elemental seismic sensor unit comprises a short subarray consisting of three seismic detectors, electrically interconnected. Each elemental sensor unit is a separate source of seismic signals. At regular intervals the analog seismic signals from the elemental sensor units are sampled in sequence and are digitized as a 20-bit binary number. The binary numbers are representative of the analog signal levels. The binary numbers are encoded in a self-clocking, return-to-zero pulse code as digital data words. The data words from the respective elemental sensor units are time-delay multiplexed into a wide band transmission channel for transmission to the central station in a constant current mode.

Abstract: An apparatus for generating a series of seismic acoustic pulses in a body of water. The series is characterized by having continuously-variable, non-repetitive time intervals between successive pulses during a continuous seismic recording. The preferred generator is an air gun comprising a variable-speed motor with a rotating cam for actuating a sleeve valve which alternately opens and closes exhaust ports in a high-pressure chamber. As the valve repeatedly opens, jets of high-pressure air are impulsively expelled into the surrounding water, thereby generating an underwater acoustic pulse train.