22 August 2000 Acoustic-to-seismic coupling and physical measurements
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At first glance, the surface of the earth appears as a relatively uniform solid surface. Seismic velocities for the earth reported in the literature are in the range of 1500 m/s and stated densities for the surface are near 3 g/m3. The big difference between the impedance of air and the surface of the earth suggests that airborne sound impinging on the surface should be efficiently reflected. During the early 1970s, personnel from Waterways Experiment Station found that geophones planted below the surface of the earth responded well to sound from aircraft. Measurements of ground motion with geophones and the signal form microphones buried in the soil as a function of soil type, depth, and frequency were conducted over a period of several years. The result of the experiments was recognition of how the porosity of soils affects the acoustic impedance of the surface and the acoustic to seismic coupling. The application of Biot theory to air filled soil pores allowed us to understand acoustic to seismic coupling in detail and enabled us to use acoustic measurements to determine soil properties. Determination of soil properties such as flow resistance, porosity and tortuosity, form acoustic measurements compare well to those determined from more conventional, non-acoustic methods. One interesting result of the measurements and theory was a confirmation of the local reaction description typically used for the impedance of soils.
© (2000) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Henry E. Bass and James M. Sabatier "Acoustic-to-seismic coupling and physical measurements", Proc. SPIE 4038, Detection and Remediation Technologies for Mines and Minelike Targets V, (22 August 2000); doi: 10.1117/12.396287; https://doi.org/10.1117/12.396287


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