Horizontally polarized shear-wave vibrator seismic source
First Claim
1. A dynamic force transducer for generating horizontally oriented shear forces and motions at a surface of a solid medium for purposes of producing dynamic shear stresses and radiating associated horizontally polarized shear waves in said solid medium, comprising:
- a rigid coupling frame for direct contact with said surface of said solid medium, said coupling frame being in uninterrupted contact with said solid medium during vibrational operation of said dynamic force transducer;
at least one pair of identical dynamic-force driver units mounted on said coupling frame to impart horizontally oriented dynamic forces having prescribed amplitude and time dependence to said coupling frame, said prescribed forces transferrable to said solid medium;
at least one pair of identical compliant springs supporting each said pair of identical dynamic force driver units mounted on said coupling frame, compliances of each said pair of springs introducing different predetermined mechanical resonances when acting in combination with the masses of said supported pairs of identical driver units and said coupling frame when excitation energy is applied to said driver units;
a means for exciting said dynamic force driver units in a manner to produce horizontally oriented forces on said coupling frame whereby one of said paired driver units imparts a horizontal pushing force and the second of the said paired driver units simultaneously imparts a horizontal pulling force equal to the pushing force, both of said forces being oriented to act along a common collinear horizontal direction; and
a means for electrically exciting said paired dynamic force driver units in a manner which imparts either continuous or pulsed oscillatory forces to said coupling frame, said continuous or pulsed oscillatory forces being prescribed in amplitude and time dependence to produce corresponding prescribed seismic shear waves in said solid medium.
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Abstract
A dynamic force transducer for generating horizontally oriented shear forces and motion at a surface of a solid medium. A rigid frame is placed in direct contact with the surface of the solid medium. At least one pair of identical dynamic-force driver units is mounted on the frame to impart horizontally oriented forces to the frame. Symmetrical pairs of compliant springs support the force drivers, but the compliances of each pair of springs may be adjusted or interchanged with other similar springs to introduce different predetermined mechanical resonances. The driver units are excited to produce the horizontally oriented forces with one or more driver units imparting a pushing force and one or more driver units simultaneously imparting a pulling force.
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Citations
21 Claims
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1. A dynamic force transducer for generating horizontally oriented shear forces and motions at a surface of a solid medium for purposes of producing dynamic shear stresses and radiating associated horizontally polarized shear waves in said solid medium, comprising:
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a rigid coupling frame for direct contact with said surface of said solid medium, said coupling frame being in uninterrupted contact with said solid medium during vibrational operation of said dynamic force transducer; at least one pair of identical dynamic-force driver units mounted on said coupling frame to impart horizontally oriented dynamic forces having prescribed amplitude and time dependence to said coupling frame, said prescribed forces transferrable to said solid medium; at least one pair of identical compliant springs supporting each said pair of identical dynamic force driver units mounted on said coupling frame, compliances of each said pair of springs introducing different predetermined mechanical resonances when acting in combination with the masses of said supported pairs of identical driver units and said coupling frame when excitation energy is applied to said driver units; a means for exciting said dynamic force driver units in a manner to produce horizontally oriented forces on said coupling frame whereby one of said paired driver units imparts a horizontal pushing force and the second of the said paired driver units simultaneously imparts a horizontal pulling force equal to the pushing force, both of said forces being oriented to act along a common collinear horizontal direction; and a means for electrically exciting said paired dynamic force driver units in a manner which imparts either continuous or pulsed oscillatory forces to said coupling frame, said continuous or pulsed oscillatory forces being prescribed in amplitude and time dependence to produce corresponding prescribed seismic shear waves in said solid medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A dynamic force transducer for generating horizontally oriented shear forces and motions at a surface of a solid medium for purposes of producing dynamic shear stresses and radiating associated horizontally polarized shear waves in said solid medium, comprising:
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a rigid coupling frame in direct contact with said surface of said solid medium, said coupling frame being in uninterrupted contact with said solid medium during vibrational operation of said dynamic force transducer; and at least one electrodynamic force driver unit mounted on said coupling frame to impart horizontally oriented dynamic forces having prescribed amplitude and time dependence to said coupling frame, said electrodynamic force driver further comprising; a horizontally oriented movable coil located axisymmetrically in a radially oriented static magnetic field produced within a body of said electrodynamic force driver unit, said coil carrying a prescribed electrical current waveform to produce either continuous or pulsed dynamic forces; a rigid horizontally oriented shaft for transferring said generated dynamic forces to reaction masses attached to each end of said horizontally oriented shaft; each said reaction mass being supported by at least one pair of identical compliant springs attached to said coupling frame, each of said springs having a compliance value which, when acting in combination with a mass of said body of said electrodynamic force driver unit and coupling frame, is capable of introducing predetermined mechanical resonances when excitation energy is applied to said dynamic force driver unit; said electrodynamic force driver body capable of producing said static magnetic field radially oriented relative to an axis of said shaft and coil and rigidly mounted on said coupling frame; said body of said force driver unit having a generally hollow cylinder surrounding said rigid horizontally oriented shaft and coil, said hollow cylinder allowing the ends of said surrounded shaft to extend out of ends of said hollow cylinder body and attached to said reaction masses to impart dynamic forces to these reaction masses, thereby causing said body of said dynamic force driver unit to experience equal and opposite dynamic forces relative those transferred to said reaction masses through electrodynamic force generation, said equal and opposite dynamic forces being transferred to said body of said dynamic force driver unit and, in turn, to said coupling frame to which said body of said force driver unit is attached. - View Dependent Claims (14, 15, 16, 17)
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18. A seismic shear wave vibrator source system utilizing a dynamic force transducer for generating horizontally oriented shear forces and motions at a surface of a solid medium for purposes of producing dynamic shear stresses and radiating associated horizontally polarized shear waves in said solid medium, comprising:
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a rigid coupling frame in direct contact with said surface of said solid medium, said coupling frame being maintained in uninterrupted contact with said solid medium during vibrational operation of said dynamic force transducer; at least one dynamic-force driver unit mounted on said coupling frame to impart horizontally oriented dynamic forces having prescribed amplitude and time dependence to said coupling frame, said prescribed forces transferrable to said solid medium; at least one pair of identical compliant springs supporting the said dynamic force driver unit and its associated components mounted on said coupling frame, compliances of each said pair of springs selectable or adjustable introducing different predetermined mechanical resonances when acting in combination with the said supported driver unit and said coupling frame when excitation energy is applied to said dynamic force driver units; a means for exciting said at least one dynamic force driver unit in a manner to produce simultaneous horizontally oriented pushing and pulling forces on said coupling frame, said pushing and pulling forces being oriented to act along a common collinear horizontal direction; a means for electrically exciting said at least one dynamic force driver unit in a manner which imparts either continuous or pulsed oscillatory forces to said coupling frame, said continuous or pulsed oscillatory forces being prescribed in amplitude and time dependence to produce corresponding prescribed seismic shear waves in said solid medium; a power amplifier capable of delivering electrical excitation voltage and current to said at least one dynamic force driver unit; and an electrical excitation signal generator capable of generating predetermined continuous or pulse waveforms to be applied to input terminals of said power amplifier, said continuous waveforms to be either a linear or a nonlinear frequency-modulated sinewave sweep signal having a predetermined amplitude versus frequency characteristic and frequency versus time sweep range, or said pulse waveforms to be either periodically repetitive or randomly timed bursts of a sine wave having a predetermined amplitude, frequency, and burst duration time, or said continuous or pulsed waveforms to consist of random noise signals having predetermined statistically determined amplitude, frequency, and time duration parameters. - View Dependent Claims (19, 20, 21)
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Specification