Abstract: A shipboard support stand for a marine vibrator of the type having characteristic revolutional shape about the vertical axis and a lower concentric guide ring surface which consists of a support ring of circumfery generally equal to the circumference of the vibrator supported by plural vertical supports above the ship's deck, and which further includes a reduced diameter locating ring secured concentrically and at lower elevation from the support ring such that the vibrator can be supported on the support ring with the vibrator guide ring closely retained within the locating ring to stow the vibrator securely.

Abstract: A device for source compensating a fiber optic coupler output automatically compensates for changes in light intensity at the output end of the fiber caused by changes in light intensity from the source, beam walking at the input of the fiber and mode changes in the fiber. Laser light enters a frequency doubler and exits as a doubled frequency output which is focused onto the input face of a fiber optic cable by a lens. The lens is selected so that the spot size of the focused light on the face of the fiber is smaller than the diameter of the fiber and that the entry angle of the light cone is within the acceptance angle of the fiber. The fiber is tightly wound into a mode scrambler to provide a uniform intensity distribution of the light exiting the fiber. The light leaving the fiber is collimated and directed to additional optical elements. The collimated beam is directed to a beam splitter which reflects 8% of the incident beam to a calibrated photodiode that is terminated with a transimpedance amplifier.

Abstract: A seismic source marine vibrator having compound hydraulic cylinders for high and low frequencies is used to generate both low frequency and high frequency acoustic pulses. Low frequency pulses are generated by operating a low frequency radiating surface and a high frequency radiating surface simultaneously. High frequency pulses are generated by operating the high frequency radiating surface alone.

Abstract: A multiple frequency range hydraulic actuator includes a low frequency cylinder with a low frequency actuator piston within. The low frequency piston operates as a high frequency cylinder having a high frequency piston within. The low frequency piston, and high frequency piston operate in conjunction to generate low frequency movement. The high frequency piston operates independently to generate high frequency movement.

Abstract: An apparatus for supporting a seismic transducer under water adjacent a towing vessel includes an elongated substantially rigid towing arm. A lower connector assembly is operably associated with the towing arm for connecting a lower end thereof to the transducer. An upper connector assembly is operably associated with the towing arm for connecting an upper end thereof to the vessel. The upper connector assembly includes a first pivot arrangement for permitting the lower end of the towing arm and the connected transducer to be lowered into the body of water. The upper connector assembly further includes a torsional support structure for resisting rotation of the towing arm about a longitudinal axis thereof. Preferably the upper connector assembly also includes a second pivot arrangement for permitting the lower end of the towing arm and the connected transducer to move laterally relative to the towing vessel.

Abstract: A marine seismic vibrator includes a housing having first and second housing portions defining an internal chamber therebetween. A hydraulic cylinder or other energizing device is connected between the first and second housing portions. The first and second housing portions are maintained in a spaced apart, non-contacting relationship. Relative motion between the first and second housing portions is provided by the hydraulic cylinder in order to generate acoustic waves in a surrounding body of water. An annular flexible seal construction is connected between the first and second housing portions for isolating the internal chamber from the surrounding body of water. This seal construction includes first and second flexible web portions sealingly connected to the first and second housing portions. A rigid hoop is connected between the first and second web portions for supporting the seal against pressure differentials between the internal chamber and the surrounding body of water.

Abstract: A hydraulic vibrator having an adjustable piston rod and a fixed piston rod to vary the cylinder volume for operation at different vibration frequencies. The adjustable piston rod is in threaded engagement with the fixed piston rod and has a piston head adjacent a piston head on the fixed piston rod. Rotation of the adjustable piston rod displaces the two piston heads, thereby varying the cylinder volume of the hydraulic vibrator.