Abstract: The invention relates to a compact tunable subsea seismic source. The source has multiple seismic radiating plates placed symmetrically about a central housing which contains a hydraulic actuating system. The source is towed to optimize the amount of energy applied to the surrounding water.

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 disclosed device is a marine seismic source which emits a constantly varying FM signal in the 10 to 100 H.sub.z range. The seismic source utilizes an adjustable length cantilever spring rotatably attached to stiff acoustic radiators, which create a signal in the water. Varying the length of the cantilever spring as a function of the frequency will permit the device to be continuously tuned for maximum power output.

Abstract: The disclosed device is a marine seismic source which produces a varying FM signal in the low end of the acoustic spectrum. The seismic source uses stiff oscillating radiators to create a signal in the water. These radiators are attached to 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: To increase the energy of seismic waves transmitted by a vibrator, one or more compliant members are connected between the driver and the base plate of the vibrator. The compliance of the compliant member is such that it is substantially rigid at the natural frequency of the vibrator, and that the natural frequency of the driven load of the vibrator is in the siesmic spectrum but is higher than the natural frequency of the vibrator.

Abstract: This invention provides for transmission of composite swept sine wave seismic signals wherein auto-correlation side lobes of such signals are reduced. The frequency spectrum of a desired swept sine wave seismic signal is divided into a number of consecutive segments, and the segments are arranged to form a sequence of segments by the order of frequency content. Component swept sine wave seismic signals each covering a segment in the sequence are generated simultaneously from the same location to produce the desired seismic signal. The component swept sine wave seismic signals are generated in a manner so that they alternate as upsweeps and downsweeps for consecutive segments in the sequence of segments. The seismic signal comprising the sum of the component swept sine wave seismic signals will have an auto-correlation function with reduced side lobes.

Abstract: A method and apparatus for improving the power output of a seismic vibrator are provided. Compliant elements with variable stiffnesses are interposed between and connected to the holddown mass and the baseplate. When the compliant elements have a first stiffness, the vibrator-earth system has a first resonant frequency. When the compliant elements have a second stiffness, the vibrator-earth system has a second resonant frequency. During sweep, the compliant elements are set on the first stiffness until the vibrator has passed through the first resonant frequency; then the compliant elements are changed to their second stiffness and the sweep continues through the second resonant frequency.

Abstract: A method and apparatus for seismic prospecting which utilizes two transducer plates that are spaced apart, with two sets of bellows placed in between and sealingly attached thereto, to transmit electrically controlled hydraulic pressure signals onto the two plates. When pressure is applied within one set of bellows, the two plates are pushed apart. When pressure is applied within the second set of bellows, the two plates are pulled together. To accomplish this pulling action of the second set of bellows, two closure plates placed between the two transducer plates are used, one attached to one transducer plate and one attached to the other transducer plate. The first closure plate is attached to the first transducer plate in such a manner that it lies between the second transducer plate and the second closure plate. By applying pressure to the second set of bellows that push apart these two closure plates, the two transducer plates are pulled towards each other.

Abstract: A hydraulic synchronizing system which comprises a double piston power source and a drain valve in fluid communication with the hydraulic lift cylinders of a vehicle mounted vibratory seismic energy source. The double piston power source supplies the hydraulic lift cylinders with substantially equal volumes of hydraulic fluid, and the drain valve adjusts the flow of hydraulic fluid out of the hydraulic lift cylinders. The system synchronizes the operation of the hydraulic lift cylinders and thus coordinates movement of the vibrator guide rods relative to the vehicle upon which the vibrator is mounted.

Abstract: A vibratory seismic energy source capable of generating significant energy over a broad frequency band. The vibrating baseplate and associated structure are designed for minimum size and weight, while retaining the structural strength to permit high actuator forces. The weight of the transport vehicle is applied to a substantially horizontal hold-down plate that is interposed between the piston-cylinder assembly and the baseplate. This horizontal plate is coupled to the baseplate through resilient means having compliance such that dynamic motion of the baseplate is decoupled from the hold-down plate and transport vehicle.

Abstract: A hydraulic stabilization system which comprises pairs of hydraulic cylinders in fluid communication connected between the vehicle support structure of the vibrator and the vibrator ground coupling plate. This configuration maintains the ground coupling plate in vertical aligment with the vehicle support structure and isolates vibratory motions of the ground coupling plate from the vehicle support structure.

Abstract: This invention is a control system for a hydraulic vibrator that permits the injection into the ground of seismic signals having pseudo-random code patterns or other broad band signals. Feedback for controlling vibrator operation is taken from the coupling plate. At low frequencies, the feedback is proportional to coupling plate position and at higher frequencies, the feedback is proportional to the coupling plate velocity.

Abstract: In a variable frequency seismic vibrator including an earth coupling plate, means for generating a reaction impedance, and an energy source for generating reciprocating movement of the coupling plate relative to the reaction impedance, the reaction impedance is generated by a reaction mass and a spring of variable stiffness which couples the reaction mass to the vibrator. As the frequency of vibration changes, the stiffness of the spring is automatically adjusted so that the impedance of the spring resonates with the impedance of the mass to maximize the reaction impedance, thereby increasing the operating efficiency of the vibrator.