Abstract: A three-axis seismic vibrator is provided which imparts compressional and shear wave seismic vibrations, either sequentially or simultaneously, into the Earth's surface. The seismic vibrator includes an earth-contacting baseplate which transmits vibrational energy into the Earth's surface; a support structure; a vibrator assembly pivotally supported at one end by the support structure; and servo-hydraulic control circuits which activate reciprocal vibration along the vibratory axis of the vibrator assembly and sustained oscillatory vibration of the vibrator assembly. The vibrations thus generated are transferred to the baseplate and injected into the Earth's surface. These vibrations and their reflections can then be recorded and analyzed to determine the mineral content of the Earth's surface in the immediate area.

Abstract: An apparatus and method for generating a seismic signal in the earth consisting of positioning a force-modulating means on the surface of the earth and then positioning a vehicle such that at least some of the weight of the vehicle is supported by the force-modulating means. At least one of the vehicle drive wheels is then rotated to cause the force applied to the earth by the force-modulating means to change thereby generating a seismic signal in the earth.

Abstract: An apparatus and a method for generating seismic waves utilizes a heavy flywheel positioned for rotation in a vertical plane to generate and store energy which is then transferred to the ground. The device includes two balanced hammers mounted on the flywheel as impact members. In operation, the flywheel is spun to a predetermined speed and then, on command, the hammers are extended outward from the flywheel so that one hammer strikes either a vertical or a horizontal strike member, thus providing a rapid transfer of a large amount of kinetic energy to the ground resulting in the generation of a set of seismic waves.

Abstract: A seismic pulse generator has a tubular outer member telescopically connected to a tubular concentric inner member. The outer member has a port in its sidewall. A force allows telescopic extension from a contracted position to an extended position. An annular well fluid chamber is located between the sidewalls of the inner and outer members in communication with the port. When at the bottom of the well, the inner and outer members are in the contracted position and the well fluid chamber has a large volume. A delay means controls the rate at which the inner and outer members initially move from the contracted to the extended position. Upon lifting the inner and outer members, the delay apparatus causes the inner and outer members to at first move apart slowly, thus allowing the inner and outer members to be raised substantially together. After a predetermined time interval, the delay apparatus allows the force to move the inner and outer members quickly to the extended position.

Abstract: The current invention is an apparatus useful for generating seismic waves with an enhanced signal to noise ratio. The enhanced signal is produced at a fundamental resonant frequency, and multiples thereof, by producing a near zero acoustic pressure condition around and beyond each end of the apparatus having an intermediate acoustic source. Such a near zero acoustic pressure condition is established preferably by either (1) using two end acoustic sources to produce a destructive interference effect with the acoustic output of a third acoustic source postioned therebetween, or (2) using two active or passive end acoustic capacitors or resonators to produce a near zero impedance condition at each end of the apparatus. The enhanced signal may be produced over a range of frequencies, including both resonant and nonresonant frequencies, by creating a high impedance condition experienced by the intermediate source and hence a high acoustic pressure around the intermediate region of the apparatus.

Abstract: The apparatus consists of a cylindrical combustion chamber supported on the top end of a cylindrical shock tube. The lower end of the shock tube is held a distance from the ground on which the apparatus is used inside a conical enclosure. The conical enclosure is attached to a circular base with a circular hole at its center. The interior of the conical enclosure is covered by a layer of acoustical insulation. The diameter of the shock tube is less than the diameter of the combustion chamber. The cone angle of the conical enclosure is about 50.degree..

Abstract: A multivibrator waveform monitoring system uses a plurality of seismic energy sources for giving vibrations to strata and a prospector, connected to a geophone, for measuring reflected vibrations. Each of the plurality of seismic energy sources includes a vibrator, a communication unit and a control unit for controlling the starting of the vibrator based on phase difference cancellation information and an operation starting instruction from the prospector. The prospector includes a communication unit and a synchronization control unit for controlling the synchronization of each of the seismic energy sources.

Abstract: A method for cascading or linking seismic vibrator sweeps to form a cascaded sweep sequence. According to the method, a first cascaded sweep sequence is generated containing N sweep segments linked end-to-end. The N sweep segments are substantially identical, except that the initial phase angle of each sweep segment within the sweep sequence is progressively rotated by a constant phase increment of about 360/N degrees. A second cascaded sweep sequence is generated consisting of (i) N consecutive sweep segments linked end-to-end which correspond to said first cascaded sweep sequence and (ii) an additional sweep segment linked to the N consecutive sweep segments which is positioned and phased so as to substantially suppress harmonic ghosts during correlation. One of these cascaded sweep sequences is used for the vibrator sweep sequence and the other is used for the correlation reference sequence.

Abstract: The current invention is an apparatus useful for generating seismic waves with an enhanced signal to noise ratio. The enhanced signal is produced at a fundamental resonant frequency, and multiples thereof, by producing a near zero acoustic pressure condition around and beyond each end of the apparatus having an intermediate acoustic source. Such a near zero acoustic pressure condition is established preferably by either (1) using two end acoustic sources to produce a destructive interference effect with the acoustic output of a third acoustic source postioned therebetween, or (2) using two end acoustic capacitors or resonators to produce a near zero impedance condition at each end of the apparatus. The enhanced signal may be produced over a range of frequencies, including both resonant and nonresonant frequencies, by creating a high impedance condition experienced by the intermediate source and hence a high acoustic pressure around the intermediate region of the apparatus.

Abstract: A source for emission of seismic energy waves into subsurface earth formations is provided with electrically energizable signal generators mounted between two plate members. One of the plate members is anchored to the earth surface and the other rests on and is coupled with the earth surface. The source is easily movable between shotpoint locations and provides controllable seismic signals of improved bandwidth and quality.

Abstract: The present invention relates to an improved downhole seismic source with an epicyclic eccentric weight system for the simultaneous generation of elliptically polarized shear wave seismic energy and compression wave seismic energy coupled into a borehole. The apparatus includes a cylindrical housing and a drive means or electric motor disposed in the housing which provides rotational output to an epicyclic eccentric weight system also disposed in the housing. Expandable tapered wedging collars are used to firmly secure the motor and the epicyclic eccentric weight systems within the housing. A flexible shaft interconnects the centerline of the epicyclic cylindrical roller and the motor whereby the roller receives the rotational output from the motor. The shaft rotates in one direction and the roller rotates in the opposite direction thereby producing an epicyclic motion.

Abstract: This disclosure is directed to a displacement amplifier for forming acoustic pulses and more particularly to one which incorporates a flexible movable lightweight diaphragm of rectangular configuration. It has upper and lower ends which are connected to opposing piston rods driven by duplicate pistons and double acting cylinders. The cylinders are located at opposite ends of the diaphragm or membrane. They are supported in an elongate tool which positions the flexible membrane in a generally rectangular window. This enables the membrane to flex as the pistons are driven, thereby enabling the flexure of the membrane to form dipole source for radially directed compression waves transmitted from the membrane in the window.

Abstract: Methods are provided for making use of an apparatus for generating vibrational energy in a borehole, the apparatus utilizes a mass and a rotary source for suspending the mass in a borehole or in casing in a borehole or in an instrument housing that may be positioned in an opened or cased borehole arranged to cause frictional contact with the surface of the rotating mass, the mass being rotatable about is rotational axis in one direction to cause it to backward whirl in the opposite direction, the centrifugal force of the whirling mass serving to generate vibrational energy that is used to obtain geophysical information as to the structure of the earth surrounding and adjacent to the borehole and for enhancing cementing and production enhancing techniques in oil or gas wells.

Abstract: An acoustic source for seismic exploration has a generally cylindrical tube ith spaced upper and lower closed ends. An insulated continuous conductor has a first portion with an exposed internal conductive end within the tube and a second portion extending therefrom through the upper end. A selectively closeable port is operably associated with the tube for permitting the tube to be filled and maintained filled with a conductive solution. A gas vent has a first open end within the tube adjacent the upper end and a second end exteriorly disposed of the tube.

Abstract: An acoustic wave energy generator comprises a body having an internal gas-pressurisable first chamber 1 adjoining a second chamber 2 into which a liquid is introduced to cover a vibratable means 4 which may be a flexible diaphragm and is mounted on the second chamber so as to close an associated opening 5 in the second chamber. After the first chamber 1 is pressurised with a first gas a common closed opening between the chambers is opened to cause communication between the chambers 1,2 to permit a shock wave emanating from the first chamber to impinge on the liquid. As a result, the vibratable means 4 is caused to vibrate so as to produce acoustic wave energy in response to the impingement of the shock wave on the liquid. By using different liquids and/or different heights of liquids in the second chamber the generator may be tuned to provide acoustic wave energy with a relatively narrow chosen frequency range or within a chosen substantially single frequency.

Abstract: A broad band seismic vibrator includes a hydraulically-operated actuator with a piston shaft depending from the actuator. A spherical member or ball is secured to an end of the shaft and received in a socket provided in an anvil. The spherical member or ball is securely clamped to the end and in its clamped condition affords the sole support for the actuator. Hydraulic means is provided for unclamping the spherical member to enable the positioning of the actuator in selected degrees of inclination from vertical and azimuth.

Abstract: Apparatus for triggering shock waves for therapeutic purposes, and generated with the aid of spark discharge in a liquid includes a signal analyzer disposed for receiving the ECG signal from a patient, a pulse generator being connected to this analyzer for sending a trigger signal shortly after the occurrence of the R peak in the ECG signal. An electromagnetically manoeuvreable, moving auxiliary electrode (14) is disposed for motion towards or into a fixed electrode gap (8, 10) in response to the trigger signal for connecting the spark gap (4, 6) to high voltage by making the electrode gap conductive.

Abstract: A downhole electro-hydraulic vertical shear wave seismic source places the reaction mass internal to the source cylindrical housing and isolates the actuator from the wellbore fluid and pressure. The clamping system of this source uses two serrated pads radiused to match the inside diameter of the casing. Hydraulic cylinders which are retracted by internal compact stacks of spring washers are used for actuating the serrated pads. A device for keeping the reaction mass in a "floating" position with actuator piston centered within the actuator cylinder is provided by suspending the reaction mass from a compact and soft urethane spring. A threaded guide rod passing vertically through this spring allows spring compression to be adjusted until the actuator piston is precisely centered with no differential hydraulic pressure across the piston.

Abstract: An apparatus for generating vibrational energy in a borehole including an elongated mass having a surface of diameter less than the borehole, a rotary source for suspending the cylindrical mass in a borehole and a system to cause frictional contact between the surface of the mass and the borehole wall, the cylindrical mass being rotatable about its rotational axis in one direction to cause the mass to backward whirl in the opposite direction within the borehole, the cylindrical force of the whirling mass serving to generate vibrational energy in the borehole.

Abstract: A human-portable geophysical energy source is disclosed having an earth-coupling element, a means for providing seismic energy operably connected to that earth-coupling element, a lower container and an upper container connected to the means for providing seismic energy, a framework that minimizes vibrations of the liquid by keeping the upper and lower containers inflexible when they are completely filled with liquid, and a hydraulic pump for filling and removing liquid from the containers. The lower container is located spatially between the earth-coupling element and the means for providing seismic energy. The upper container is located spatially above the means for providing seismic energy. The liquid provides mass to impart energy through the earth-coupling element and to maintain coupling with the earth.

Abstract: The present invention relates to methods of seismic exploration utilizing vibrationally generated, elliptically polarized shear waves in an earth medium for subsequent detection of one or more dimensions of orthogonal particle motion. The invention relies upon a shear wave source of a type which couples a continually rotating longitudinal force into an earth medium thereby to propagate an elliptically polarized shear wave for refraction, reflection or subsurface detection, various forms of exploration being well within the capabilities.

Abstract: Seismic signals are generated in an earth formation at a selected point in a wellbore by apparatus insertable in the wellbore at the distal end of a tubing string. The apparatus is adapted to receive hydraulic pressure fluid from the tubing string for deploying contactor pads in engagement with the wellbore wall and for transmitting seismic signals through the pads to the earth formation. In one embodiment a hydraulic piston is directly connected to linkage for the contactor pads and an oscillatory signal is imposed on the piston for generating vibratory seismic signals. In a second embodiment, a compressed gas-driven impactor is moved to and held in a cocked position by a hydraulically-actuated setting and latching mechanism. Hydraulic control valves and electrical operating circuits are disposed on the apparatus and may be controlled from the surface by way of a wireline cable extending through the tubing string.

Abstract: A downhole seismic energy source for use in generating a seismic signal in a borehole including an elongated mass having a generally cylindrical surface of diameter less than the borehole, an actuator suspending the cylindrical mass in the borehole wherein the cylindrical surface thereof is in frictional contact with the borehole wall, the cylindrical mass being rotatable about its rotational axis to cause the mass to whirl within the borehole in the direction opposite the direction of the rotation of the mass, the mass cylindrical force serving to create a seismic energy signal.

Abstract: Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C.

Abstract: A downhole hydraulic seismic generator system for transmitting energy wave vibrations into earth strata surrounding a borehole. The system contains an elongated, unitary housing operably connected to a well head aboveground by support and electrical cabling, and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The system further comprises a hydraulic oscillator containing a double-actuating piston whose movement is controlled by an electro-servovalve regulating a high pressure hydraulic fluid flow into and out of upper and lower chambers surrounding the piston. The spent hydraulic fluid from the hydraulic oscillator is stored and pumped back into the system to provide high pressure fluid for conducting another run at the same, or a different location within the borehole.

Abstract: An acoustic signal transmitter for well logging tools and the like comprising a housing having a generally rectangular opening formed therein and defining a fluid filled cavity in which a compliant sheet transmitter member is disposed and is provided in a relaxed condition with a curvature. Opposite ends of the transmitter member are connected to piezoelectric actuators which are responsive to an electrical signal to elongate to stretch the sheet into a generally planar state to generate a pressure pulse in the cavity for transmission through a fluid filled borehole to a formation for, preferably, measuring the shear wave velocity in the formation material.

Abstract: A vibrator and method for transmitting seismic signals into the earth to obtain data on various subsurface characteristics. The vibrator is driven with piezoelectric transducers, and can produce better signal resolution at higher frequencies than is possible with hydraulic vibrators. The piezoelectric vibrators can be used in various embodiments at the earth's surface, within a borehole, or while permanently buried in the earth.

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: One or more seismic sources impart seismic pulses into the earth in a coded sequence. The coded sequence is composed of a minimum of three cycles of a Galois sequence of order N, where N is a positive integer. The response of subsurface formations to the coded sequence is obtained and correlated with one cycle or the outgoing Galois sequence of the same order. Correlation properties of the Galois sequences provide a way to sum a large number of seismograms that are superimposed in time, improving the signal to noise ratio while keeping the field time in which the seismograms are obtained to a minimum. Using this encoding technique, responses of subsurface formations to concurrent activation of each of several sources can be obtained and separated from each other.

Abstract: A sound source capable of generating high energy acoustic pulses is lowered into a well borehole. A chamber of high pressure air in the source provides the energy for the pulses. A firing mechanism in the source is armed using increased pressure on the drilling mud in the well borehole. The pressurized mud is stored in a chamber in the source having closable ports. When the firing mechanism is operated, the ports are open, forcing the mud from the source into the borehole mud column and causing a cavitation zone in the mud at the ports. When the cavitation zone collapses, an acoustic energy pulse is formed. Pulses may be formed in this manner at the same depth or a number of depths in the well bore during a single run of the source in the well.

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: An assembly is provided for generating seismic signals in the earth utilizing one or more shells. A tubular barrel made of frangible material, such as plastic, has a shell positioned within it, the shell having a head with an electrically actuated primer button. A continuity block is positioned within the barrel providing electrical continuity with the shell and the primer button. Conductors are connected to the continuity block and extending exteriorly of the barrel, the shell being fired by connecting the conductors to a voltage source. The barrel may be elongatd to house a plurality of spaced apart shells, the first shell being electrically fired and the other shells being fired by percussion. Each percussion shell is engaged by a plunger which is actuated by the slug fired from the adjacent shell so that upon firing of the electric shell, the slug thereof fires the first percussion shell and each percussion shell thereafter is fired in sequence.

Abstract: A vibrator and method for transmitting seismic signals into the earth to obtain data on various subsurface characteristics. The vibrator is driven with piezoelectric transducers which can operate below 500 Hz, and can produce better signal resolution at higher frequencies than is possible with hydraulic vibrators. The piezoelectric vibrators can be used in various embodiments at the earth's surface, within a borehole, or while permanently buried in the earth.

Abstract: An electromagnetic vibrator for seismic and civil-engineering applications is provided with a supporting structure fitted with a coupling element, and a reaction mass, which is to be caused to vibrate, with an electromagnetic drive associated therewith and provided at least with electromagnetic coils. The reaction mass is magnetically suspended on the supporting structure by means of one or more magnets with the associated electromagnetic coils and is at the same time caused to vibrate by the electromagnetic drive. The vibration force is exerted on the pole surface of the one or more magnets and the reaction mass is accelerated to at most the acceleration due to gravity.

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: A controlled implosive downhole seismic source having a substantially hollow closed vessel body adapted to be lowered in a borehole and means for selectively causing at least a portion of the vessel body to implode under pressure thereby producing seismic waves.

Abstract: Multiple downhole seismic signals are generated by an apparatus comprising one or more elongated rod segments insertable in a borehole and provide with spaced-apart predetermined lengths of Primacord explosive charge helically wrapped on the exterior of the rod segment and spaced apart by circumferential baffles supported on the rod segment. The charges are selectively fired through a motor actuated selector switch and a switch stepping and firing circuit including only two conductors and blocking diodes for imposing signals of opposite polarity on the selector switch and its actuating motor.

Abstract: A stilt structure for a vibrator assembly in which the spider members on each end of the actuator are pivotally coupled to the vertical supports (stilts). The pivotal connection allows rotation of each component thereby eliminating induced bending moments between the spider members and the vertical supports.

Abstract: A seismic signal generator with a self-adjusting footprint base plate. A signal generator for use on paved or other hard surfaces, has a pair of tread members (preferably urethane) that are laterally slidable with respect to the reaction mass. The tread members are biased outwardly away from the reaction mass. Should slippage from the point of initial placement occur during signal generation, the biasing force will continue to move the tread members outwardly to a more stable position, thereby achieving optimum intimate contact between the generator and the surface of the ground maximizing signal transfer into and through that surface.

Abstract: A sweep generator for a seismic source vibrator provides for any one of a variety of sweep signals governed by input parameters. Selected analytic functions may be entered which are solved to provide a plurality of sweep parameters. The sweep parameters may also be directly entered by the operator. The time and frequency sweep parameters (or time and amplitude) are then employed to generate polynomial coefficients for consecutive use in a polynomial equation. The polynomial equation is repeatedly solved to generate a series of instantaneous frequencies or instantaneous amplitudes which are applied to an analog wave synthesizer. The analog wave synthesizer then generates an approximation to the desired sweep signal for input to the hydraulic system of the vibrator.

Abstract: In the art of acoustic well sounding a gas-gun for the sudden discharge of a measured quantity of compressed gas, comprised of two chambers, viz. a discharge chamber closed at one end by a poppet, and on the opposite end by a power-head, the latter a cylinder including a sealed piston, with the poppet connected by sealed piston rod penetrating the cylinder head, and terminated at the piston. The entire assembly to be so proportioned that regardless of the position of the piston of gap remains between the piston and the cylinder-head penetrated by the piston rod. Means for connecting this gap to the inside of the discharge chamber through a check valve permits gas flow from the discharge chamber to the gap, but no in the reverse direction, and means for venting the gap to the atmosphere. A passage from the opposite side of the piston to the axial outlet of the discharge chamber, a spring or a positive locking device for pressing the poppet against the valve seat.

Abstract: An impact tool for linearly accelerating a mass such as in a jack hammer. The tool includes first and second members respectively mounted in sealing relationships in first and second outlets of a chamber. The chamber is initially pressurized with a first quantity of gas which remains constant during the normal operation of the tool. To begin a cycle, the first member is moved toward the second member to sealingly engage the end portions thereof and entrap a first volume of gas therebetween. The volume of the entrapped gas is then reduced by continuing to move the first member. This raises the pressure of the entrapped gas and opens a one-way check valve to place the entrapped gas in fluid communication with the gas in the surrounding chamber. Forward movement of the first member is then stopped which again seats the check valve wherein movement of the first member is reversed so that it moves away from the second member.

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: This invention is an improved type of shear wave vibrator are carried by a support vehicle and utilizing telescoping tubes for energy engagement within an underlying earth medium. A shear wave vibrator so constructed is particularly desirable for use over marshy or soft surface earth areas. The device consists of a jack assembly supporting a shear wave vibrator relative to a suitable carrier vehicle in vibrationally isolated manner. The vibrator structure consists of a pair of parallel, elongatable telescoping blades for earth penetration and engagement with a passive reaction mass pivotally secured across the top portion of the telescoping blades and an active mass/vibrator system pivotally secured across the lower portion of the telescoping blades adjacent the earth surface.

Abstract: A seismic source consists of an electroacoustic transducer having a metallic structure, shaped like an empty round paraboloid (1) closed at the base by means of an elastic diaphragm and filled with a proper liquid. Around the focus of the paraboloid two main electrodes (5) are set and an auxiliary electrode (6) is put between the first ones. The main electrodes (5) are connected to a set of capacitors (C.sub.o) supplied by a high-voltage power supply (HT). One of the main electrodes (5b) and the auxiliary electrode (6) are connected to a trigger pulse generator (EHT) driven by a remote control (4) via a synchronization pulse generator (3). The discharge between the main electrodes (5) primed by a preliminary spark, generates an acoustic pulse through the liquid medium of the transducer on the ground where the paraboloid (1) is engaged. So the transducer generates seismic waves utilized for shallow prospecting both on land and underwater.

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: The present invention is a downhole seismic source capable of generating seismic forces in excess of 1000 newtons. The source produces seismic waves for seismic applications, particularly cross borehole measurements and vertical seismic profiling. Coupled with motion sensing devices, the present invention also performs as a seismic logging tool. The source is comprised of an outer housing, a means for clamping the source securely to the wellbore, and a linear electromagnetic actuator which utilizes permanent magnetic material having remanent magnetic field exceeding about 0.9 T such as rare earth permanent magnetics. The source has a diameter of about 12.5 cm to fit within a typical wellbore and the actuator has a length of about 1 meter.

Abstract: A seismic source is disclosed which is particularly useful for generating horizontally polarized shear waves in the earth for seismic surveying. It comprises an elongated, hollow, substantially vertical cylinder having an earth-contacting pad pivotally mounted to its lower end by a horizontal pivot shaft extending parallel with the front-to-back centerline of a transport vehicle. The lower surface of this large rigid pad contains multiple, blade-like teeth extending parallel with the pivot shaft for gripping the earth's surface for transmitting powerful horizontally polarized shear stress impulses into the earth. The cylinder contains a slidable piston-like reaction mass. The bottom of the cylinder is a strong upwardly diverging conical surface serving to focus and direct upwardly the discharge blast from each port of an air gun extending horizontally and with the axis of the air gun being oriented parallel with the pivot axis and being located a short distance above the pivot shaft.

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.