Abstract: An improvement for the drive control system of a vibratory sound source used in seismic exploration comprising apparatus for generating a feedback signal proportional to the instantaneous acceleration of the reaction mass structure of the sound source's hydraulic drive system. Degenerative feedback of the signal so developed is used to reduce distortion of the vibratory seismic signal imparted into the earth.

Abstract: The invention relates to a nondestructive downhole seismic source capable of generating S.sub.V -waves, S.sub.H -waves, and P-waves alone or in combination to determine information about a surrounding geologic formation. The invention also includes processes of performing crosswell tomography and reverse vertical seismic profiling. The invention also includes a means and process to carry out in hole seismic logging operations.

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 hydraulically controlled seismic energy source for impressing individual seismic energy pulses into the ground, wherein the hydraulic pressure forcing the ram downwardly is substantially reduced slightly before the ram contacts the ground, and a continual upward hydraulic force is applied to a downwardly facing surface of the ram, whereby the ram is quickly removed from the ground after a seismic impulse is generated to prevent secondary contact between the ram and the ground.

Abstract: The present invention is an improvement to conventional baseplates for imparting seismic energy to an earth formation. A baseplate typically has a plurality of downwardly disposed triangular prism-shaped cleats for engagement with the earth surface above an earth formation under seismological investigation. At least one leaf spring is supported about midway along its length from the lower surface of the baseplate and between the cleats. An elongate horizontal ejector member is slidably interconnected to the respective ends of the spring. In operation, as the baseplate is lowered into engagement with the earth surface the ejector member is moved upward and the leaf spring is compressed. When the baseplate is lifted upward the restoring force of the leaf spring results in a generally downward force against the ejector member.

Abstract: The present invention provides a method and apparatus for controlling the response of a seismic vibrator during its actuation period. The sweep input signal is modified in response to an average of the force applied to the earth by the vibrator over at least one cycle of the sweep signal. Additionally, this modified drive signal may be further adjusted by selective adjustment of the amplitude of the signal within selected frequency ranges.

Abstract: Multiple vehicle-transported impact-type surface seismic sources designed to shoot along slant paths to create combined compressional and shear wave pulses in the earth are provided with radio controlled actuators. The azimuth of each shooting path is automatically referenced to magnetic north so that signals of equivalent wave form contents are produced despite vehicle misalignments and without reliance upon individual vehicle operators.

Abstract: A baseplate for a seismic vibrator is formed from two identical cast plate members having stiffening ribs and alternating plug and socket cones along the ribs. The cast plate members are arranged together to align opposed plug and socket cones of the plates and are connected by attaching mechanisms passing through holes in the aligned cones. The aligned cones accomplish a wedging or clamping action on each other when the plate members are connected.

Abstract: Method and apparatus for downhole seismic exploration employing vibration emanating from a point deep in a well. An elastic steel column has an upper end extending above the top of the well. A reaction mass is attached vertically thereabove through a vertically mounted compression spring system, in parallel with it a vertically mounted servo-controlled hydraulic cylinder-piston assembly. The displacement of a spear or bit on the lower end of the column relative to earth develops a displacement signal. The piston in the hydraulic cylinder is under reciprocated servo control to apply vertical vibration to the upper end of the column and thereby to the spear, while developing an electrical, pressure-differential signal corresponding to the pressure across the cylinder-piston assembly.

Abstract: A vibrator seismic source has a sweep generator for providing a pilot signal and sensors for generating a feedback signal representative of the force imparted to the ground by the vibrator pad. Circuitry is incorporated for separating the fundamental signal from the feedback signal and for separating the distortion from the feedback signal. Means are provided for generating a control signal for controlling the action of the vibrator means. Included are means for reducing the amplitude of the pilot signal a designated amount, determined by the distortion, and means for algebraically summing the reduced amplitude pilot signal and the fundamental signal to provide an error signal. The error signal is input to a loop filter to perform real time correction of the control signal. The reduced amplitude pilot signal is input to means for adjusting the control signal for trends in the distortion.

Abstract: A vibrator baseplate for use in a seismic signal transducer system has a bottom plate with a dome centrally located thereon. A pair of partial domes overlap the central dome on opposite sides thereof. Top plates are attached to the partial domes, which are also attached to the bottom plate. Internal rib stiffeners are provided within each dome and gusset members extend between the partial domes and the top plates. Means are provided to connect the baseplate to the seismic signal transducer system. Alternatively, the baseplate comprises a bottom plate with an elongate eccentric dome attached thereto.

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 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 vibratory seismic surface source includes a hydraulic vibrator the energy of which is coupled into the earth through a ground contacting base plate. The vibrator is supported above and independently of the base plate so that it may be pivoted about a first rotational axis within a truck-mounted gimbal-type frame which itself is tiltable about a second horizontal rotational axis perpendicular to the first. After the vibratory axis is oriented in the desired direction the vibrator is lowered so as to contact a suitably contoured upper surface of the base plate. Inclination of the vibrator is accomplished by "push-pull" operation of pairs of oppositely-directed hydraulic cylinders.

Abstract: A dual mode vibrator assembly for selectively generating either pressure wave or shear wave signals in the earth has a single inertia mass with a plurality of vertically parallel offset cylinder bores and at least one horizontal cylinder bore extending therethrough. Each cylinder bore reciprocably retains a piston member and is in fluid communication with a fluid source. The lower ends of the vertical piston members are connected to a base plate to generate pressure waves. A foot member is connected to each end of the horizontal piston member and interconnected by anti-roll rails in sliding relationship with the inertia mass. Cleats are connected to the bottom of each foot member to engage the earth for generating shear waves. A manifold directs fluid from a servo-valve either to passages leading to the vertical cylinder bores for pressure wave operation or to the horizontal cylinder bore for shear wave operation.

Abstract: A dual-mode vibrator for alternately injecting P-waves and S-waves in the earth including a hydraulically driven shaker assembly, a ground-contacting base plate, and a jacking means for raising and lowering the base plate relative to a vehicle. The shaker assembly is supported above, and coupled to the base plate by a supporting means. The supporting means has a first configuration for coupling the shaker assembly to the base plate for generating P-waves and a second configuration for pivotally coupling the shaker assembly to the base plate and to a rigid member associated with the vehicle for injecting S-waves.

Abstract: A mixed device for successively generating in the earth, at the same location, longitudinal and shear waves is disclosed. The device comprises in association a target coupled to the earth surface and having a first striking face substantially parallel thereto and at least one second striking face substantially perpendicular to said first striking face. A guide tube is adapted to be positioned above the first striking face and perpendicularly thereto, and a movable weight is slidable in the guide tube and adapted to strike the first striking face. At least one hammer is articulated to a support rigidly secured to the guide tube and adapted to strike one second striking face of the target. Directional coupling means connect the guide tube to the target in such a manner that the weight sliding in the guide tube directly impinges the first striking face, but such that the guide tube is substantially released from the effect of the hammer impact on a second striking face.

Abstract: A target member of the seismic energy source is driven into ground surface engagement, as the vehicle, to which the seismic energy source is pivotally connected, moves, due to the target member geometry, that is by resolving the tractive force so that the force driving the target member into the ground is a vector directed at an angle less than 90.degree. to the direction of the vehicle movement. Impulses from an impulse generator are transmitted to the target member after the latter has been driven into the ground, during the vehicle movement or at rest. The impulses are transmitted to propagate in a plane parallel to the ground surface and perpendicularly to the direction of the target member movement.

Abstract: The improved device for generating acoustic shear waves in the earth comprises a target member adapted to be coupled with the earth and provided with two lateral striking surfaces on which impinges a hammer pivotably mounted on a platform; the target member is connected through damping means to a cage supporting the platform, the hammer and its actuation means, said cage being displaceable with respect to the frame of a carrying vehicle between a position of contact with the earth of the target member and a lifted position thereof, the striking surfaces being inner walls of the target member.

Abstract: The claimed invention is directed to seismic exploration wherein an earth surface vibrator sweeps through a frequency range with varies with time as a function of frequency.

Abstract: A reaction mass and hydraulic cylinder assembly for a seismic transducer. A hydraulic biasing cylinder (76) is formed between a lower piston rod (32) and a reaction mass (44) and is located below a hydraulic drive cylinder (46). The lower piston rod (32) includes a first portion (36) and a detachable second portion (38-40), the detachable second portion forming an upward facing shoulder (42) which partially defines the hydraulic biasing cylinder (76). The hydraulic drive cylinder (46) is formed by a cylinder sleeve (48) and upper and lower cylinder bushings (50 and 52) having lower and upper ends (54 and 56), respectively, concentrically received within the cylinder sleeve (48) to define the upper and lower ends, respectively, of the hydraulic drive cylinder.

Abstract: A movable inner cylindrical valve member is rigidly attached to the upper end of an air powered impact projectile designed for striking a target to produce an acoustic pulse. By seating upwardly within the bore of a fixed outer valve member against spaced apart tapered valve faces, the cylindrical wall of the inner valve member covers intermediate air pressure ports in the bore wall. In operation, the axial separating movement between the inner and outer valve members will instantly admit air pressure adjacent the closed end of the bore of the outer valve member in order to exert an accelerating force to drive the projectile. At the same time, the operation of this valve can be made essentially pressure independent by proper selection and placement of the annular seals which contact the valve faces.

Abstract: Apparatus for generating an acoustic pulse in a medium wherein an impact piston is driven downwardly along a cylindrical housing by compressed gas to strike a rigid target positioned in contact with the earth. In its firing position, the tapered upper portion of the piston extends above the top of the housing within a container occupied by the compressed gas, the top of the piston being at the same time recessed within a gastight mating enclosure at the top of the container. In this position, the tapered piston surface is constantly exposed to circumferential gas pressure so as to provide a positive breakaway force. Upon release of suitable piston latch means, the piston is first urged downwardly by this breakaway force and thereafter accelerated more powerfully when the top of the piston separates from the enclosure and becomes exposed to gas flow uniformly from all directions.

Abstract: A vibratory seismic energy source capable of generating significant energy over a broad frequency band. The vibrating baseplate and associated structure are designed to have minimum weight while still retaining sufficient structural integrity to permit the use of high actuator forces. This, coupled with a large reaction mass results in the generation of significant energy levels in the earth at high frequencies.

Abstract: A dual mode vibrator (DMV), in its hydraulic cylinder, automatically provides a shorter stroke for higher frequencies and a longer stroke for lower frequencies. The cylinder contains a pair of sleeves, each sleeve having one diameter portion sufficient to slideably engage the piston and having a smaller diameter portion to slideably engage the piston rod. The sleeves themselves are moveable within the cylinder, such movement being effected by the application of high pressure on one end or the other. When the sleeves are moved together, the stroke is effectively shortened. When the sleeves are moved apart, the stroke is effectively lengthened.

Abstract: A seismic testing apparatus is provided in which linear motion or excitation of a horizontally disposed table is achieved simultaneously along three mutually orthogonal axes by means of independently operable hydraulic-actuator assemblies. Rotational or torsional motion of the table about the linear excitation axes is resisted by separate, mechanical rotation-inhibiting means each consisting of a torsionally rigid structure disposed parallel to the table and perpendicularly to their respective associated axes of excitation. The torsionally rigid structures are each connected to the table at two spaced-apart points, with all four points of connection lying in the same plane.

Abstract: Method and apparatus for measuring the acoustic impedance of a surface in which the surface is used to enclose one end of the chamber of a Helmholz resonator. Acoustic waves are generated in the neck of the resonator by a piston driven by a variable speed motor through a cam assembly. The acoustic waves are measured in the chamber and the frequency of the generated acoustic waves is measured by an optical device. These measurements are used to compute the compliance and conductance of the chamber and surface combined. The same procedure is followed with a calibration plate having infinite acoustic impedance enclosing the chamber of the resonator to compute the compliance and conductance of the chamber alone. Then by subtracting, the compliance and conductance for the surface is obtained.

Abstract: A variable frequency seismic pulse is produced by releasing a weighted piston within a partially evacuated cylinder. The piston compresses residual air in the cylinder before striking a base plate held firmly in contact with the ground. Controlling the pressure of the gas remaining in the cylinder controls the frequency and amplitude of the seismic pulse applied to the ground. The seismic pulse can be applied at various angles from vertical from a thumper mounted on a vehicle or from a hand-held thumper.

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: A releasable heavy mass is provided which is capable of producing by impact with the ground a shock which can be used in seismic prospecting.This mass is characterized by the fact that it comprises very many individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact, and in that its base is of considerable area relative to the surface of the whole mass and is maintained substantially plane at least after release and up to impact. The mass is, in seismic prospecting, released from a helicopter.

Abstract: A transportable, acoustic pulse generator is described employing an impact mass suspended above a freely movable target plate positionable on the ground, the impact mass being forceably propelled downwardly to strike the target plate to generate an acoustic pulse adapted for seismic purposes. The generator housing is adapted to be mounted on the rearwardly extending rails of a conventional transport truck. In order to eliminate bouncing of the truck due to generator housing recoil on firing, the housing itself is jacked up by lift cylinders extending upward from the target plate so as to minimize or eliminate the spring suspension of the truck. Upstanding sleeve guides carried on the generator housing cooperate with the lift means to provide lateral stability and to establish a precise vertical separation between the impact mass and the target plate, thus insuring repeatable signal energy content and timing.

Abstract: The invention relates to a method and device for detecting changes in the mechanical state of the members of a structure implanted in the sea, whereby each member is subjected to impacts and after each impact, the simultaneous signals of excitation and dynamical response of the member are recorded, the signals of identical frequency being processed in order to define a ratio which varies with the frequency and presents peaks. The aforesaid operations are repeated at regular intervals, a watch being kept for any shifts in the peaks which could indicate a change in the structure.

Abstract: A mobile generator for producing waves for seismic exploration. A hammer, mounted on an elongated boom, is dropped to strike an anvil embedded in the ground to create a ground wave. The boom is pivotal between positions selected according to the nature of the wave to be created. A pair of hydraulic piston actuators move the boom between its selected positions. A tensioning device is connected to the cable which drops the hammer in such a manner as to prevent the hammer from rebounding after an impact.

Abstract: A hydraulic drive system for an underwater vibrator has a hydraulically driven mass for generating a seismic wave into the seabed. The hydraulic drive system for the vibrator is accomplished by filtering sea water, conveying the filtered sea water to the hydraulic pump where the sea water under pressure is supplied through a control valve to the hydraulic vibrator. The output from the control valve is coupled to the sea water. The hydraulic system provides hydraulic fluid which will not need to be cooled, thereby eliminating the normal cooling system along with several necessary accumulators and sump which are used in a closed hydraulic system.

Abstract: A rotating eccentric weight apparatus and method for generating coded shear wave signals for use in seismic exploration. The apparatus includes a rotatable eccentric and a position sensor capable of detecting each instant that the eccentric passes a particular angular position about its axis of rotation and generating a code signal for use in correlating the raw seismic data obtained. In one embodiment, the apparatus includes an outrigger shovel which transmits a sinusoidal shear wave signal generated by the rotating eccentric while the rest of the apparatus is caused to alternately decouple from and impact against the earth surface to transmit a coded train of pressure wave impulses into the earth.

Abstract: A releasable heavy mass is provided which is capable of producing by impact with the ground a shock which can be used in seismic prospecting.This mass is characterized by the fact that it comprises very many individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact, and in that its base is of considerable area relative to the surface of the whole mass and is maintained substantially plane at least after release and up to impact. The mass is, in seismic prospecting, released from a helicopter.

Abstract: The present invention relates to a torsional shear wave generator for producing clean horizontally polarized seismic shear waves that can be utilized in investigating the earth's subsurface. Basically the torsional shear wave generator of the present invention comprises a hollow elongated shaft having a plurality of circumferentially spaced vanes radially projecting therefrom. Secured to a top portion of the shaft, as normally positioned in the ground, is a loading arm that extends generally perpendicular to the longitudinal axis of said shaft. In some cases, the central shaft is not necessary if the vanes can be joined by other means such as welding.

Abstract: A method of seismic exploration and a system which provides the capability for increasing the number of depth points from which seismic data are acquired are disclosed. This increase in data is realized without increasing the number of recording channels or the number of geophone stations employed in the system. A higher common depth point multiplicity is achieved by separating energy sources in relation to geophone stations. The recording system is capable of automatically sorting out the data from different energy sources and storing it in different blocks of a memory. Since substantially all available recording time is fully utilized by using energy sources to their optimum efficiency, higher common-depth-point multiplicity can be achieved with minimum field costs.

Abstract: In accordance with the present invention, an impulse generator of high portability is provided using a pair of guillotinized, separately activated hammer/anvil sub-assemblies. Since each sub-assembly is horizontal positioned, say in contact with the earth from a position below the wheel of an exploration truck, the equivalent of the "flying blade" of a guillotine, i.e., a weighted hammer element, must be provided with horizontal movement. This is done by tensioning a plurality of springs attached between the hammer element and a rectangular main frame.During cocking and release of the hammer, the explorationist is provided with a series of visual signals in the form of deactivated and activated panel lights. These signals are automatically provided by controller means of the present invention. Release of the cocked hammer, however, is operator controlled for safety reasons say by activation of a latching means attached to the main frame of the assembly.

Abstract: A rotating eccentric weight apparatus and method for generating coded shear wave signals for use in seismic exploration. The apparatus includes a rotatable eccentric and a position sensor capable of detecting each instant that the eccentric passes a particular angular position about its axis of rotation and generating a code signal for use in correlating the raw seismic data obtained. In one embodiment, the apparatus includes an outrigger shovel which transmits a sinusoidal shear wave signal generated by the rotating eccentric while the rest of the apparatus is caused to alternately decouple from and impact against the earth surface to transmit a coded train of pressure wave impulses into the earth.

Abstract: A mobile device is used which includes a target-member adapted for coupling to the earth and a means for striking the target- member so as to generate acoustic shear waves.The target-member is coupled to the earth through a deformable coupling member secured to the rigid frame of the target- member, the coupling being enhanced by the combination of a suction means and a network of channels arranged on the face of the coupling member which is in contact with the earth, whereby a partial vacuum is created between the coupling member and the earth.

Abstract: A mobile generator for producing seismic waves in the ground, which includes a mobile four-sided frame, a boom having its lower end pivotally connected to the frame, and a worm gear mounted on the frame such that by rotating the worm gear about its longitudinal axis, the boom is pivoted toward a selected impact position. A hammer, mounted on the boom, is raised and then dropped toward an anvil carried beneath the frame on the ground. The anvil has several impact-receiving surfaces such that either a P wave or a shear wave can be generated by pivoting the boom and without relocating the anvil.The anvil structure is positioned on the ground by applying a major portion of the weight of the apparatus on the anvil plate.

Abstract: A mobile device for generating acoustic shear waves comprises a structure provided with at least one axle with wheels mounted thereon, said axle being displaceable with respect to at least a part of the structure.The mobile device has mounted thereon a target-member displaceable from a position suitable for transportation to a working position where it is in contact with the earth, and means for striking the target member, when in working position, by means of a mass, to produce an impact thereon.The target member is provided at its upper part with tracks for the wheels of the axle so that the wheels can be driven, by displacing the respective axles, from a position of contact with the earth to a position where they bear on the target member with the weight of at least a part of the structure.

Abstract: A vibratory seismic energy source capable of generating significant energy over a broad frequency band. The vibrating baseplate and associated structure are designed to have minimum weight while still retaining sufficient structural integrity to permit the use of high actuator forces. This, coupled with a large reaction mass results in the generation of significant energy levels in the earth at high frequencies.

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 mobile generator for producing waves for seismic exploration. An elongated boom guides a wave-generating hammer along a linear path of motion to strike an anvil embedded in the ground, the boom being movable between several adjusted positions including a vertical position for generating a P wave, an inclined position for generating a shear wave, and a horizontal position for transport. An improved anvil for generating either a P wave or a shear wave is also disclosed.

Abstract: A seismic exploration method in which a rotating eccentric weight seismic source is employed to transmit a coded energy signal into the earth. A position sensor mounted on the source directly detects the instants at which the rotating eccentric passes a particular angular position about its axis of rotation, and generates a code signal which is used to correlate the raw seismic data. Preferably the source is allowed to decouple from the earth surface such that the coded energy signal transmitted into the earth is a coded impulse train.

Abstract: Apparatus for generating combined compressional and shear wave signals in the earth which employs a seismic source, such as a cylindrical gas exploder, having a free-moving wedge shaped base which tapers symmetrically downwardly to a thin blade. When the exploder is fired at an angle inclined to the vertical, a force is generated along its longitudinal axis which drives the base downwardly in the same direction so as to propagate seismic signals having a compressional component and a shear component. The blade is disposed transversely to the direction of the horizontal component of this applied force. The penetration achieved by the thin blade portion of the base insures sufficient earth coupling to generate high energy shear seismic signals and minimizes horizontal translation of the exploder under a wide range of soil conditions.

Abstract: Apparatus for generating vibrations in a medium, such as the ground, comprises a first member which contacts the medium, means, preferably electromagnetic, which includes two relatively movable members for generating vibrations in the apparatus and means operatively connecting the said two members to said first member such that the relatively amplitudes of the movements of said three members can be adjusted to match the impedances of the apparatus and the medium.

Abstract: A device for generating acoustic waves in the earth by striking a mass, housed in a guiding tube, against a target member secured to the lower end of this tube and coupled to the earth in operating conditions, including means, such as an electromagnet, for holding said mass at the upper end of said tube and releasing it at will, and means to turn the tube upside down after each operation so as to reset the mass in position for a new operation.