Geophysics: Attenuation of Shear and Compressional Waves in Pierre Shale*
F. J. McDonal, F. A. Angona, R. L. Mills, R. L. Sengbush, R. G. Van Nostrand, J. E. Whiter, 2000. "Geophysics: Attenuation of Shear and Compressional Waves in Pierre Shale", Seismic Wave Propagation: Collected Works of J. E. White, J. E. White
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Attenuation measurements were made near Limon, Colorado, where the Pierre shale is unusually uniform from depths of less than 100 ft to approximately 4,000 ft. Particle velocity wave forms were measured at distances up to 750 ft from explosive and mechanical sources. Explosives gave a well-defined compressional pulse which was observed along vertical and horizontal travel paths. A weight dropped on the bottom of a borehole gave a horizontally-traveling shear wave with vertical particle motion. In each case, signals from three-component clusters of geophones rigidly clamped in boreholes were amplified by a calibrated, wide-band system and recorded oscillographically. The frequency content of each wave form was obtained by Fourier analysis, and attenuation as a function of frequency was computed from these spectra.
For vertically-traveling compressional waves, an average of 6 determinations over the frequency range of 50–450 cps gives ∝=0.12 f. For horizontally-traveling shear waves with vertical motion in the frequency range 20–125 cps, the results are expressed by ∝ = 1.0 f. In each case attenuation is expressed in decibels per 1,000 ft of travel and f is frequency in cps. These measurements indicate, therefore, that the Pierre shale does not behave as a visco-elastic material.
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Seismic Wave Propagation: Collected Works of J. E. White
This first chapter sets the stage for the later technical development of Dr. Whit’s career in applied seismics. Experiments, f’wst at the Acoustics Laboratory of the Massachusetts Institute of Technology and later at Mobil Oil and Marathon Oil, provided insight into the general problems of impedance measurements, transduction, filtering, and attenuation. These papers also serve as a bridge to show geophysicists how theft own experiments in seismology naturally interface with (indeed, arose out of) the larger world of sound measurements in air and water. These experiments demonstrate the power of geometrically constrained experiments to allow verification of approximate (and in some cases, exact) theories of sound.