Abstract: A seismic source signal generator includes a mass, a primary accumulator and a secondary accumulator, the secondary accumulator having an internal volume smaller than an internal volume of the primary accumulator. A method for generating a signal using a seismic vibrator includes operating the seismic vibrator using hydraulic fluid, damping hydraulic pressure deviations in the hydraulic fluid using a first accumulator in hydraulic communication with the hydraulic fluid, and damping pressure deviations in the hydraulic fluid using a second accumulator in hydraulic communication with the hydraulic fluid, the second accumulator having an internal volume smaller than an internal volume of the first accumulator.

Abstract: A multilayer backing absorber for use with an ultrasonic transducer comprises an elemental multilayer having at least one metal layer and at least one adhesive layer, wherein the backing absorber is adapted to be coupled to a vibrating layer of the ultrasonic transducer.

Abstract: A method for simultaneously operating multiple seismic vibrators using continuous sweeps (little or no “listening” time between sweeps) for each vibrator, and recovering the separated seismic responses for each vibrator with the earth signature removed. Each vibrator is given a unique, continuous pilot signal. The earth response to the motion of each vibrator is measured or estimated. The vibrator motion records for each vibrator and the combined seismic data record for all the vibrators are parsed into separate shorter records. The shorter records are then used to form a system of simultaneous linear equations in the Fourier transform domain, following the HFVS method of Sallas and Allen. The equations are then solved for the separated earth responses.

Abstract: A method of processing seismic data obtained using a seismic vibrator that includes estimating travel times of direct wave arrivals between the seismic vibrator and an array of seismic receiver locations and wavefield deconvolving the seismic data using the direct wave arrival travel times. Also a related method of producing a high-frequency geological subsurface image that includes acquiring seismic data having significant harmonic energy using a seismic vibrator, estimating direct wave arrival travel times between the seismic vibrator and an array of seismic receiver locations, wavefield deconvolving the seismic data using the estimated direct wave arrival travel times, and using the wavefield deconvolved seismic data to produce a high-frequency geological subsurface image. A further related computer useable medium having computer readable program code means embodied therein practicing the inventive method.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: An imaging guidewire can include one or more optical fibers communicating light along the guidewire. At or near its distal end, one or more blazed or other fiber Bragg gratings (FBGs) directs light to a photoacoustic transducer material that provides ultrasonic imaging energy. Returned ultrasound is sensed by an FBG sensor. A responsive signal is optically communicated to the proximal end of the guidewire, and processed to develop a 2D or 3D image. In one example, the guidewire outer diameter is small enough such that an intravascular catheter can be passed over the guidewire. Techniques for improving ultrasound reception include using a high compliance material, resonating the ultrasound sensing transducer, using an attenuation-reducing coating and/or thickness, and/or using optical wavelength discrimination. Techniques for improving the ultrasound generating transducer include using a blazed FBG, designing the photoacoustic material thickness to enhance optical absorption.

Abstract: The invention relates to a device for emitting seismic vibration waves mountable on a movable platform (100) comprising a vibration system for transmitting the waves into the ground and a system for supporting a device (200) on the ground, wherein the system for supporting on the ground is fixable to the movable platform (100) and transfers a charge to a ground-mounted vibration system in a ground support direction (1). Said ground-mounted vibration system is fixable to the system for supporting on the ground by compensation means (251, 252, 253) for compensating perpendicularity defects between the ground general plane and the around support direction (1).

Abstract: An oscillation generator for seismic applications includes a housing in which two coils are housed, both coils being acted upon with alternating current or electrical impulse and permanent magnets, and which is coupled via a coupling element to the object to be examined. The coils of the oscillation generator are each borne on a center leg of a packet of sheets cut in an E-shape, the free legs of the sheets associated with respective ones of the coils pointing away from one another. The coils are coupled to a block that can be linearly displaced in the housing. Securely attached to the side walls of the housing on a non-magnetic plate are permanent magnets that are disposed in the extension of the free end of the legs of the sheets, and the polarity of the exterior permanent magnets is reversed relative to the center permanent magnet.

Abstract: This document discusses, among other things, an imaging guidewire that includes one or more optical fibers communicating light along the guidewire. At or near its distal end, one or more blazed or other fiber Bragg gratings (FBGs) directs light to a photoacoustic transducer material that provides ultrasonic imaging energy. Returned ultrasound is sensed by an FBG sensor. A responsive signal is optically communicated to the proximal end of the guidewire, and processed to develop a 2D or 3D image. In one example, the guidewire outer diameter is small enough such that an intravascular catheter can be passed over the guidewire. Techniques for improving ultrasound reception include using a high compliance material, resonating the ultrasound sensing transducer, using an attenuation-reducing coating and/or thickness, and/or using optical wavelength discrimination.

Abstract: The present invention is a method of processing seismic data in which one or more seismic vibrators are activated with one or more pilot signals and vibrator motions are recorded along with seismic data. Vibrator signatures are computed from measured vibrator motions, such as the ground force signal. A desired impulse response is specified from either a measured vibrator motion or from test data or field data from a location near the location from which the seismic data was acquired. A deconvolution filter is computed from the impulse response and the vibrator signature. Alternatively, a single separation and deconvolution filter is derived from the impulse response and from vibrator signatures from multiple vibrators and sweeps. The deconvolution or deconvolution and separation filter is used to process the seismic data. The vibrators are then moved to a new location, and the activation is repeated.

Abstract: A device for seismic emission in an underground formation comprising one or more vibrators of any type and method for implementing same. According to a preferred embodiment, each vibrator comprises at least one pillar (1) of sensitive elements (of piezoelectric type for example) between two end plates or slabs (2, 3) and a signal generator for applying vibrational signals to the pillar. The pillar (1) is coated with a protective sheath (4) and the vibrator is positioned in a well or cavity (W) and embedded in a mass of a solid coupling material (7) in contact with protective sheath (4) and the two end plates (2, 3) over at least part of each of the respective faces thereof, which provides coupling of the vibrator with the surrounding formation. The vibrators can be buried at intervals in relation to one another in a well. Sequential triggering thereof with selected delays allows reinforcement of the waves emitted by the device in a preferred direction.

Abstract: The present invention relates to a polymer electrolyte membrane fuel cell with a water removing structure capable of improving a performance of the fuel cell itself due to water removing efficiency higher than that of a conventional fuel cell. It is an object of the present invention to provide a vibration generator removing water using vibration and sound unlike the prior arts to activate an electrochemical reaction and a polymer electrolyte membrane fuel cell having a more compact and efficient water removing structure by comprising the vibration generator.

Abstract: This invention is a method of separating induced microseismicity signals from seismic signals acquired within active seismic monitoring operations carried out in underground zones under development which has application for monitoring of underground hydrocarbon or fluid storage reservoirs. Seismic records are formed from signals emitted by one or more seismic sources controlled by orthogonal signals. In this case, the signals are processed to separate the respective contributions of the at least one seismic source to the signals received and to reconstruct the seismograms equivalent to those that would be obtained by actuating the at least one seismic source separately.

Abstract: The method for exploring desired characteristics of a subsurface sector, having at least one resonant frequency, is based on selectively transmitting suitable narrowband energy waves into the subsurface sector, thereby producing narrowband signals reflected off the subsurface sector. The transmitted narrowband energy waves can be selectively and optimally adjusted in real time so as to provide optimum illumination of the desired characteristics from the explored sector.

Abstract: An oscillation generator for seismic applications includes a housing in which two coils are housed, both coils being acted upon with alternating current or electrical impulse and permanent magnets, and which is coupled via a coupling element to the object to be examined. The coils of the oscillation generator are each borne on a center leg of a packet of sheets cut in an E-shape, the free legs of the sheets associated with respective ones of the coils pointing away from one another. The coils are coupled to a block that can be linearly displaced in the housing. Securely attached to the side walls of the housing on a non-magnetic plate are permanent magnets that are disposed in the extension of the free end of the legs of the sheets, and the polarity of the exterior permanent magnets is reversed relative to the center permanent magnet.

Abstract: The invention relates to an apparatus and method for imparting a precise amount of impulse energy to be delivered to the ground. The apparatus includes an anvil for operative deployment against the earth a hammer operatively connected to the anvil for striking the anvil; and a control system operatively connected to the hammer for controlling the impulse energy of the hammer striking the anvil. The control system includes a linear feedback system for measuring the linear position of the hammer with respect to the anvil during a force stroke and a processor for receiving linear position data from the linear feedback system for controlling the relative speed of the hammer with respect to the anvil during a force stroke through an actuation system.

Abstract: A method and related apparatus are described for generating acoustic signals for use in a vibratory seismic survey, including the step of combining into a drive signal a high frequency sweep signal, which sweeps upwardly through a high frequency band during a first time interval, and a low frequency sweep signal which is of lower amplitude than the high frequency sweep signal and which sweeps upwardly through a low frequency band during a second time interval, wherein the second time interval starts during the first time interval but after the beginning thereof; and applying the drive signal to a mechanical drive system for a vibratable element. The method improves the utilization of a single vibratory source.

Abstract: A plurality of actuators are provided at predetermined intervals on the reverse surface of a predetermined side wall of a swimming pool. When an electric signal corresponding to a sound to be propagated in the water is given to the actuators, the electric signal is converted by the actuators into a mechanical vibration signal to cause vibrations. The actuators are secured directly to the reverse surface of the predetermined side wall by an adhesive or otherwise, and thus the vibrations of the actuators are radiated as a sound in the water of the pool through the side wall.

Abstract: A vibration generator can be used for seismic applications, producing vibrations for exploration of near-surface subsoils up to 150 meters. Containing two coils activated with AC current or other electrical pulses, the generator is coupled to the object to be investigated by suitable elements. Inside is an inner housing, the outer housing movably supporting, on opposing sides, two coils connected through the inner housing. One coil is activated continuously and alternates with a positive wave component of an AC current control signal; at the same time the other coil alternates with a negative wave component. The result, a controlled vibratory motion, is also achieved with DC voltage. Because of the law of action and reaction, the vibratory motion passed to the coupling elements allows motion into the object being investigated. In contrast to conventional moving coil systems for electromechanical vibration transduction, this generator is based on a soft-metal magnetic instrument.

Abstract: Method, apparatus and article of manufacture for monitoring and characterizing the operation of a transducer (i.e., motor or pump) downhole. In particular, transducer RPMs are determined by analysis of acoustic information. An acoustical source (signal generator) located on a downhole tool (e.g., a drill string) creates acoustic energy which is received and processed by a receiving unit, which may be located at the surface of a wellbore. The acoustical source is operably connected to the transducer, so that the frequency of the signal produced by the acoustical source corresponds to the speed of the transducer. The acoustic signal of the acoustical source may then be isolated from other acoustical energy produce by downhole equipment, such as a drill bit. Having determined transducer speed by isolation of the acoustic signal, other operating parameters may be determined. Illustrative operating parameters include torque, flow, pressure, horsepower, and weight-on-bit.

Abstract: The present invention provides a system for, and method of determining an azimuth of a seismic energy source. In one embodiment, the system includes a directional assembly having a mount configured to be coupled to a seismic energy source, a rotatable mass assembly coupled to the mount, a compass rose coupled to one of the mount or the rotatable mass assembly and a direction reference coupled to the other of the mount or the rotatable mass assembly. The compass rose is registered with the direction reference to provide a direction orientation of the rotatable mass assembly with respect to the mount.

Abstract: This invention relates to a level-measuring device in which a signal generating device, a sampling device and a transmitting and/or receiving device are optimally connected to one another for various applications and signal shapes. The signal generating device generates both a radio-frequency transmit signal and a sampling control signal for sampling the radio-frequency signal. The sampling device, the signal generating device and the transmitting and/or receiving device being connected by a coupling device which comprises one of: a transformer; at least one line node; a &lgr;/4 coupler and a circulator.

Abstract: The invention relates to a vibroseis analysis method in which frequency-sweep signals (10) are emitted into a subsurface, the signals reflected on the substrata of such a subsurface (10, 20) are logged and the logged signals are processed, a method in which the harmonics (20) of the fundamental signal (10) initially emitted are eliminated from the logged signals, by applying the steps consisting in: a) providing a time/frequency plot, showing the respective contributions of the fundamental (10) and of the harmonics (20) in the logged signal, b) providing a time/frequency plot also showing these contributions of the fundamental (10) and of the harmonics (20) in the logged signal, this plot having been stretched in the direction of the frequency axis such that the fundamental (10) of this plot is over the location of a harmonic (20) chosen from the plot; c) adapting the power amplitude of this stretched plot to make this amplitude correspond to that of the said chosen harmonic (20) of the plot; d) subtracti

Abstract: Provided is a vibrating section having an ultrasonic transducer of piezoelectric elements and a rear ultrasonic horn and a front ultrasonic horn, the horns being joined to the transducer. The ultrasonic transducer has a consumption power set at 8W or less. The ultrasonic horn has a flat front end surface, the area of the front end surface being set at 0.07 to 1 cm2.

Abstract: A seismic shear wave generator comprising a seismic wave source (3) arranged on a base plate (11) arranged for being placed at the seabed, and a coupling device (1) arranged for coupling the wave source (3) mechanically to the seabed in order for shear waves to be transmitted to the seabed. The novelty of the invention is as follows: a cylindrical skirt (1) closely arranged along the base plate's (11) circumference and extending down from the underside of the base plate (11), and open downwards, and a pump device (2) arranged for pumping water respectably out of, and into, the skirt (1) and form vacuum or overpressure, respectively, in a closed cavity formed by the skirt (1) and the base plate (11) and the seabed (1) is lowered onto the seabed. By means of the device mentioned above the shear wave generator may be suctioned fixed to the sea bed and thus transfer shear waves via the skirt (1) to the seabed.

Abstract: A logging tool having a tool body, which can be positioned in a fluid-filled borehole, including a receiver section and a dipole transmitter; wherein the dipole transmitter includes a transducer with a shell having a reaction mass and a motor located therein, the motor operatively connecting the shell and the reaction mass such that only an outer surface of the shell is in contact with the fluid in the borehole. This new type of dipole source for well logging involves shaking all or part (axially) of a dipole tool body to produce a pure, broadband acoustic dipole signal while at the same time coupling as little energy as possible into the tool body. Important variations on this idea include a linear phased array of shaker sources, and active cancellation of tool borne noise.

Abstract: A non-contact vibrometer is employed to measure seismic energy imparted to the earth by a land vibrator.

Abstract: A vibration wave detector having a first diaphragm for receiving vibration waves, such as sound waves and so on, to be propagated in a medium, a resonant unit having a plurality of cantilever resonators each having such a length as to resonate at an individual predetermined frequency, a retaining rod for retaining the resonant unit, a second diaphragm positioned on the opposite side of the first diaphragm with respect to the retaining rod, and a vibration intensity detector for detecting the vibration intensity, for each predetermined frequency, of each of the resonators, by the vibration waves received by the first diaphragm and propagated to the resonant unit through the retaining rod.

Abstract: A system for geophysical exploration uses a single source (30) which emits signals over multiple octaves. The source is driven by a composite sweep signal having two or more sweeps, one of which covers the lower octave (10) while the other sweeps cover the remainder of the bandwidth. The signals covering the lower portion are reduced in the case of a sweep which varies linearly with time in proportion to the square root of the ratio of the sweep rate of the signals covering the upper end to the sweep rate of the signals covering the lower end. The signals are transmitted simultaneously. Because of the composite sweep the same energy spectrum is transmitted as with a sine wave sweep which extends over the entire frequency band, while reducing the peak power and radiator displacement required at lower frequencies to maintain a flat spectrum. The size of the equipment can be reduced.

Abstract: A seismic vibrator system for imparting compressional and shear wave vibrations into the earth has an earth contacting base with a vertical post. A tubular hub is slidably received on the post in a piston/cylinder relationship. Spaced apart horizontal top and bottom plates are secured to the hub. A mass is slidably supported between the plates. Pistons interconnect the hub and the mass. Hydraulic energy is used to reciprocate the mass vertically on the post and horizontally between the plates.

Abstract: Seismic exploration for hydrocarbons may use an eccentric-mass (or "swinging-weight") vibrator as the seismic source. According to the invention, a vibrator undergoes alternate periods of acceleration and deceleration, during one of which the vibration may be annulled. For example, the rotating mass may be formed in a plurality of parts; then the several parts are disposed in a manner that rapidly and automatically balances their vibratory forces during the period when the vibration is to be annulled, and that adds their vibratory forces during the other period. The invention further provides for modulation of the frequency-time relation during deceleration, for synchronization of several vibrators, and for modulation of the effective output force by controllable variation of the mass, eccentric radius or relative phase of the several parts of the rotating mass; in such modulation, only resultant forces are applied to the vibrator bearings.

Abstract: Disclosed is a system for decomposing an original signal of arbitrary frequency content into a user determined plurality of signals, each of which signals is centered about a variable center frequency. The system of the present invention utilizes a Bank of a plurality of combination Phase Lock Loop and associated Band Pass Filter Bank Components, the Center Frequency of a Frequency Pass Band of each of said Band Pass Filters being effected by use of a signal input thereto, and output by, an associated Phase Lock Loop. The present invention system is particularly well suited for application in the compensation of vibrations in a physical system as sensed by sensors located therein to sense feed-forward and/or feed-back vibration signals.

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: A removable bore liner is provided that substantially increases the dependability, flexibility and field-serviceability of seismic vibrators and other hydraulically actuated devices. A method for installing the removable bore liner in a seismic vibrator is also provided.

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: A method for producing simple seismic wavelet shapes with minimal side lobe energy for use as reference signals for seismic vibrators is disclosed.

Abstract: A sweep frequency vibrator is set forth. It has an elongate cylindrical housing closed at the top and bottom ends. On the interior, there is a reactionary mass fixed to identical upper and lower piston ends. They are received in seal isolated chambers, one being formed in a moveable plug. The plug is moved to thereby vary the spacing of the chambers. As the frequency is changed, plug is moved to assure sufficient clearance from the excursion of the reactionary mass. Hydraulic oil under pressure is delivered to control valves, one for each piston end. The two control valves and piston ends have very short flow lines. Moreover the excursion permitted for the plug assures operation without bottoming out.

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: 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 SH wave generating apparatus includes a driving plate (1) of increased rigidity; a fixing device (6) provided on the bottom of the driving plate for fixing the driving plate onto the earth's surface; a plurality of hydraulic actuators (2) mounted on the driving plate, which have reaction masses and act tangentially on the same circumference from the center of the driving plate; and a driving device (4,5) for reciprocating the plurality of hydraulic actuators (2) at a controlled frequency, thereby generating transverse waves. The plurality of hydraulic actuators (2) are equidistantly mounted on the driving plate (1), and each include a cylinder (2) and a piston rod extending therethrough. The said piston rod is mounted at both ends on supports (3) fixed to the driving plate (1) and the cylinder acts as a reaction mass. Alternatively, the piston rod extending through the cylinder 2 may be provided at both ends with reaction masses.

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: A detection system for monitoring safety equipment being worn by an individual for whom the wearing of such equipment is mandatory. The detection system is more specifically directed to individuals who are passing through an entryway into a designated area which requires the wearing of the equipment, and also to operators of machinery which require the same. In one embodiment, the detection system includes an infrared reflector which is fixed to a designated piece of equipment, for example, safety eyewear, an infrared transmitter and an infrared receiver which are located at one side of an entryway to the designated area and an alarm system which is activated when a person who is not wearing the specified equipment attempts to pass through the entryway into the designated area.

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: 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: 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: Apparatus for generating a controlled parameter elliptically polarized shear wave into an earth medium. The apparatus consists of a baseplate for engagement with the earth medium in omni-directionally resistant manner and a reaction mass and actuator assembly affixed thereto and energizable to impart reciprocal lateral forces to the baseplate that exert a predetermined resultant force at a controlled rate of rotation.

Abstract: Air wave noise caused by a vibrating baseplate on a seismic vibrator is reduced or eliminated through passive absorption of sound. In passive absorption, reduction of air wave noise is achieved by building a rigid, light-weight enclosure for the baseplate which remains isolated from the induced ground vibrations and nonresonant.

Abstract: The present invention relates to a method for generation of elliptically polarized shear waves in an earth medium using two shear wave vibrators engaged to the earth medium in cross-polarized attitude and driven at sweep rates having variable phase displacement.

Abstract: In a method of seismic exploration using swept-frequency signals, compressional and shear waves are emitted simultaneously. Typically the waves are generated by swinging-weight vibrators acting through a single baseplate. If the frequency of the shear vibration is one-half that of the comopressional vibration, the downward vertical forces can be phased to minimize the horizontal slippage of the baseplate. The sensitive axis of the geophones is inclined to the vertical for detecting both compressional waves and shear waves. For defined ranges of sweep rate, separate compressional and shear records are obtained by cross-correlating the geophone signal separately against the vertical and horizontal emissions.

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.