Q-MEASUREMENTS FROM COMPRESSIONAL SEISMIC-WAVES IN UNCONSOLIDATED SEDIMENTS

Several processing methods in both time and frequency domains have been used to compute the in-situ specific dissipation function 1/Q, or its inverse, the quality factor Q, in water-saturated unconsolidated sediments. These methods are based on measurements of spectral amplitude ratio, peak-to-peak and first-peak amplitude ratio, rise time, pulse broadening, and the Futterman causal attenuation operator of an attenuating signal. Compressional seismic waves were generated from explosive sources ranging in size from 1 to 64 mg of silver azide and recorded at a depth of 7. 62 m below the surface near Wendover, Utah. The medium consisted of silty sandy clays with mean grain size diameter of 7. 48 mu m and water saturation of 70 percent. The hydrophone receivers were spirally distributed at distances ranging from 25 to 200 m from the source.