Abstract: An acoustic wave generator for telemetering signals through a drillstem comprises a sub interposed in the drillstem with a central mandrel and a piston mass disposed in sleeved relationship around the mandrel and reciprocable by hydraulic pressure fluid to impose reaction forces on the mandrel and the drillstring at selected frequencies to transmit acoustic waves through the drillstring. A control system for operating the generator includes a hydraulic pump, a control valve and a frequency control circuit which operates the control valve to effect reciprocation of the piston mass at selected frequencies for transmitting serial data from the control system through the drillstring to a receiving system. The generator is coaxially arranged in the drillstring and is operable to generate high-energy acoustic wave signals for propagation through relatively long drillstrings.

Abstract: A method of seismic exploration is disclosed wherein a signal recording obtained from subsurface geophone receivers placed below the weathered layer is used to characterize the waveform of the downgoing signal generated in the earth by a surface seismic source. The reflections of the source signal measured at the earth's surface at a point remote from this source are then deconvolved with an operator derived from the subsurface waveform in order to eliminate or compensate for the filtering effect of the weathered layer. Successive measurements of the downgoing source signal are taken at the earth's surface as the source is advanced along a seismic line. One of such surface signals can be combined with the subsurface signal recording in order to derive a transfer function indicative of such filtering effect for the intervening weathered layer.

Abstract: A method and an apparatus for mass retrieval for an acoustic pulse generator are disclosed herein. In an impulse type seismic generating apparatus an air spring, mechanical spring, controlled pressurization of an air spring or other energy storage medium is employed to use potential energy to raise the impact mass to a resting position above an earth contacting baseplate as quickly as possible after the impact mass strikes the baseplate.

Abstract: A method of seismic exploration uses recordings from both surface receivers and buried sensors to determine the full elastic effect of the near surface layer on an applied seismic wave. The surface receivers are arranged relative to the seismic source location so that rotational effects may be detected. Buried sensors are located so that vertical effects may be detected. This full elastic effect may be used in subsequent seismic data acquisition to reconcile the effect of the near surface so that the response of the underlying rock formations may be known.

Abstract: Seismic signal generating apparatus of the impact type that includes a signal generator having an impact mass therein, a base plate or coupling member that is engaged by the impact mass to generate the signal, a housing attached to the generator that encircles the impact mass and extends toward the base plate, and means for excluding water from within the housing so that the impact mass travels only through gas prior to engaging the anvil. The apparatus also includes control means for positioning the generator angularly and azimuthally.

Abstract: A downhole seismic generator that can be located in various positions in the well including being located in engagement with the bottom of the well bore and that includes a large striker mass driven by compressed gas into engagement with an anvil having one end located in engagement with the medium in which the seismic signals are to be set up. Retractor means is provided to return the mass to the ready position so that a series of seismic signals can be provided as desired. Optional baffle means connected to the generator prevent waves from traveling through the well bore which would otherwise diminish or confuse the seismic shock wave initially generated.

Abstract: Alignment restoring apparatus for use with seismic shock generators that includes a support frame, a lift frame supported by the support frame, a seismic generator peripherally supported by the lift frame, and a base plate supported by the life frame and arranged to be impacted by the seismic generator. The alignment restoring apparatus includes biasing means located between the lift frame and the base plate to provide a restoring force upon movement of the frame relative to the base plate whereby the initial relationship between the frame and base plate is re-established assuring that the time lapse from initiating the propulsion of the seismic generator toward the base plate to the time of impact therebetween is repeatable.

Abstract: A coupling member for coupling forces generated by a seismic transducer into an elastic medium, such as the earth, wherein the coupling member includes a plurality of discrete cleat members that project downwardly from the lower surface of the coupling member and each of the cleat members has lateral sides, including arcuate portions arranged generally tangent to the sides and to the lower surface of the coupling member whereby the elastic medium is compressed, thereby preventing movement of the coupling member.

Abstract: The improved seismic vibration apparatus includes variable length control means located so as to effectively and efficiently position the vibrator relative to the base plate and apparatus to isolate the vibrator from the control system and from the vehicle frame so that effective seismic vibration is imparted into the base plate and consequently into the earth.

Abstract: An impact type surface seismic source powered by compressed air includes an elongated piston which moves within the bore of a cylindrical firing tube suitably mounted above an earth contacting target. The firing tube consists of two or more tubular sections slidably joined in telescopic relation. When the piston is allowed to fall from a cocked position, compressed air enters the bore above the piston through side ports and drives the piston downwardly. At the same time, the inner sliding section or sections of the firing tube are exposed to the same air pressure within the bore and are also driven downwardly. In this way, the bore of the firing tube lengthens automatically to provide a longer stroke for the piston and thus a greater attained kinetic energy of impact for a given operating pressure as the piston reaches the target. The apparatus is designed for mounting on a transport vehicle so that the firing tube itself may be raised in operation and lowered for reduced vehicle profile during transport.

Abstract: A baseplate assembly for an impulsive, vehicle-transported seismic wave generator for use on rocky, irregular earth surfaces is comprised of a small diameter, earth-contacting, freely movable target member which is laterally confined in the center of a surrounding wide area frame adapted to support vehicle weight directly against the earth. Such a target member may safely be subjected to high dynamic loading per unit area responsive to the impact of a descending mass.

Abstract: Three-component three-dimensional seismic data is acquired by locating a plurality of receivers off the seisimic shot line of a seismic source. The angle between the seismic shot line and a line extending between the seismic source and each receiver is used to normalize the signals generated by the two shear wave detectors in each receiver by mathematically rotating the orientation of the receiver and the orientation of the seismic source to produce horizontal shear wave signals and vertical shear wave signals generally equivalent to those that would have been produced if each receiver and seismic source were aligned along a seismic shot line.

Abstract: An impulsive seismic generator is mounted on a swamp buggy suitable for operations both in a marshy environment and on land. The generator employs a target plate which may be lowered into a body of water or mud beneath the buggy so as to contact subsurfaces of varying degrees of firmness. The submerged components of the generator are surrounded by a water-tight barrier which isolates the space between a descending mass and the receiving target plate from the surrounding fluid.

Abstract: A man-portable, easily disassembled seismic source is described which utilizes a self-propelled projectile. The projectile, carrying a container of compressed gas, is supported over a rigid earth-contacting target at one end of a lightweight linear guide or track. When the support is removed, the container is automatically vented to atmosphere in an upward direction. In this way, the projectile is jet-propelled to the target, which in turn produces an acoustic pulse in the earth.

Abstract: The weight of a transport vehicle and the actuator of an impact type seismic source carried thereby is partially transferred by means of hydraulic lift cylinders to a freely movable earth contacting baseplate positioned beneath the actuator. In operation a mass is propelled by the actuator along a prescribed slant path to strike the baseplate. Shear strain is induced in elastomeric pads sandwiched between the hydraulic lift cylinders and the baseplate if the baseplate shifts sideways under such a slanting blow. The pads then exert a force to restore the vehicle and the actuator to a correct perpendicular alignment over the baseplate. Upper and lower position locator means fixed respectively to the hydraulic lift cylinders and to the baseplate interface with the elastomeric pads and fit slidably within each other so as to transmit vertical force from vehicle to baseplate.

Abstract: A vibratory seismic surface source includes a single vibrating mass, the energy of which is coupled to the earth through a ground contacting base plate. Means are provided for varying the inclination and azimuth of the vector path traversed by the reciprocating mass, such that any desired combination of compressional and shear waves, both SH and SV type, may be generated and recorded simultaneously at a point on the earth's surface remote from the source.

Abstract: An impact-type surface seismic source utilizing a closed air system includes a heavy pistons supported above an earth contacting base plate partially within a hollow upstanding cylindrical housing, having a closed top and an open bottom. The housing side walls are provided with ports which communicate with a source of high pressure air. Preparatory to a firing operation, the piston blocks these ports, but upon a firing signal the piston is released and falls under gravity permitting high pressure air to enter the bore of the housing through the ports, thus driving the piston downwardly to strike the base plate. As the piston is retrieved and nears its original position, blocking the side ports, it mechanically actuates a valve so as to vent any air trapped above the piston within the housing bore. The vent remains open until the piston again falls.

Abstract: A vibratory seismic surface source includes a single vibrating mass, supported above and independently of an earth-contacting base plate. Means are provided for varying the inclination and azimuth of the vibrator axis. After the vibrator is oriented in any desired direction, it is then lowered along its vibratory axis so that it bears directly against the hemispherically concave upper surface of the base plate. When the vibrator is actuated in this position of contact, any desired combination of compressional and shear waves, both SH and SV type, may be generated and recorded simultaneously at a point on the earth's surface remote from the source.

Abstract: A full waveform seismic source is described which is adapted to propel a heavy mass powerfully downward against the surface of an earth-contacting target plate. Means are provided for rotating the barrel of the actuator about two mutually perpendicular horizontal axes so that energy can be delivered to the earth along a plurality of preselected slant paths. In this way, any desired combination of compressional and shear waves, both SH and SV type, may be generated at a point on the earth's surface. The target is contoured so that any slant path followed by the accelerating mass always impacts the target normal to its surface.

Abstract: A full waveform seismic source is described which is adapted to propel a heavy mass powerfully downward against the surface of an earth-contacting target plate. Means are provided for rotating the barrel of the actuator about two mutually perpendicular .[.horizontal.]. axes so that energy can be delivered to the earth along a plurality of preselected slant paths. In this way, any desired combination of compressional and shear waves, both SH and SV type, may be generated at a point on the earth's surface. The target is contoured so that any slant path followed by the accelerating mass always impacts the target normal to its surface.