Abstract
Abstract A novel approach using digital processing is described for the study of shear-wave velocities and attenuation anisotropy in some sedimentary rocks and a slate. Broadband ultrasonic pulses in the frequency range 0.3–0.6 MHz for polarized shear waves are transmitted through the specimen to be characterized for comparison with a reference (aluminium) having low attenuation. The attenuation is calculated in terms of the quality factor Q from the Fourier spectral ratios, using a digital signal processing technique. Experimental results are presented and discussed for measurements made on two anisotropic rocks (a slate and a sandstone) and isotropic samples (a limestone and a granite). The observed attenuation anisotropy is generally accompanied by anisotropy in velocity. Compared with the magnitude of the velocity, the magnitude of the shear wave attenuation is more sensitive to changes in anisotropy and grain size. These laboratory observations are expected to be helpful in the interpretation of seismic and acoustic well logging data.
Published Version
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