The experimental evidence is very convincing that seismic waves experience an exponential attenuation in which the coefficient varies as the first power of frequency. Stated another way, earth materials are characterized by a loss parameter Q which is independent of frequency. Several nonlinear stress-strain relations have been proposed in the literature, each of which would agree with the above experiments. The stress-strain relation to be discussed here can be related to static friction and sliding friction at areas of contact between grains, for a loose granular material. In this paper, the relation should be taken as a pure assumption, whose worth rests on the resulting properties of the medium under vibration and stress.
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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.