Many measurements have been made on fluid-saturated porous rods executing extensional, flexural, and torsional motion. Measurements for extensional and flexural motion yield a loss parameter for Young’s modulus waves Qy, and the measurement for torsional motion yields Qs for shear waves. Qp has then been calculated for compressional waves in bulk rock, on the assumption that the fluid-saturated rock is an isotropic solid. I point out the fallacy of computing Qp from these measurements and also urge workers to recognize the losses due to simple fluid viscosity i?terpreting their data on extensional waves in rods. By application of published theory, I show that peaks in attenuation of extensional waves are to be expected at frequencies of several hertz to several kilohertz, depending upon rod radius. Computed curves are compared with published measurements on Navajo sandstone saturated with water, ethanol, and n-decane. In each case, computed peak frequency agrees with published measurements. Shift of the peak frequency with temperature from 4°C to 25°C is due to change of viscosity of the saturating fluid (water).
Figures & Tables
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.