Seismic Waves—Field Studies
Just as experiments in the laboratory are the key to understanding wave propagation in its simplest settings, experiments in the field are the key to understanding wave propagation in more complicated media. Even the earliest of these studies (Velocity measurements in near-surface formations, 1953) showed the importance of including the effects of anisotropy, as would be echoed in an experiment 30 years later aimed specifically at characterizing the anisotropy of the Pierre shale (1983). This first paper in 1953 also showed the value of the Hertz-Mindlin contact theory in describing the increase of velocity with depth in homogeneous, unconsolidated sediments. Anisotropy appears again in “Seismic waves from a horizontal force,” where polarization-dependent shear-wave velocities (i.e. shear-wave splitting) are encountered. Shear-waves were experimentally demonstrated to be excited by explosive sources (1963). Dr. White noted the extra attenuation (relative to P-waves) that are experienced by the S-waves. An earlier experiment, again on the Pierre shale (1958) also gave experimental values for the attenuation of P- and S-waves in a relatively homogeneous shale unit. Dr. White also produced some work related to the tools that field geophysicists use. In “transient behavior of patterns” (1958), there is a discussion of arrays of detectors, while “Motion product seismograms” (1964) describes a means of combining three-component data to determine source direction.
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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.