Attenuation of seismic waves in dry and saturated rocks: I. Laboratory measurements

Abstract

The attenuation of compressional (P) and shear (S) waves in dry, saturated, and frozen rocks is measured in the laboratory at ultrasonic frequencies. A pulse transmission technique and spectral ratios are used to determine attenuation coefficients and quality factor (Q) values relative to a reference sample with very low attenuation. In the frequency range of about 0.1–1.0 MHz, the attenuation coefficient is linearly proportional to frequency (constant Q) both for P‐ and S‐waves. In dry rocks, [Formula: see text] of compressional waves is slightly smaller than [Formula: see text] of shear waves. In brine and water‐saturated rocks, [Formula: see text] is larger than [Formula: see text]. Attenuation decreases substantially (Q values increase) with increasing differential pressure for both P‐ and S‐waves.

Effect of Partial Water Saturation on Attenuation Characteristics of Low Porosity Rocks

“…Compressional wave velocity changes little until the pore spaces are fully saturated with water because the air in partially saturated pore fluids diminishes the stiffness of the pore fluids and hardly contributes to strengthening the rock frame. On the other hand, when there is an increase in water saturation, the compressional wave attenuation-that is related to energy dissipation-tends to increase more sensitively than velocity (Gardner et al 1964;Toks} oz et al 1979;Mavko and Nur 1979;Murphy 1982;Winkler and Nur 1982;Cadoret et al 1998).…”

Regional variations of seismic attenuation from coda and Lg waves in northern Baja California

“…Some authors have correlated the quality factor Q with properties which characterize the lithosphere, such as stress [Lockher et al, 1977], pressure [Toksoz et al, 1979] For that area specifically, we performed another study which will be discussed in another paper (Dominguez et al, submitted manuscript, 1996). For larger areas there is a lack of measurements of attenuation, although northern Baja California is a very active area capable of generating moderate size earthquakes such as the Victoria earthquake of June 1980, ML = 6.1 [Reyes, 1980].…”

Measurements of shock-induced guided and surface acoustic waves along boreholes in poroelastic materials

“…This method uses the output for the frequency-dependent phase velocities from the conventional FFT-Prony method, 26 as the input for the spectral ratio technique. 27 This extra step significantly improves the determination of the specific attenuation Q −1 . It is worthwhile to mention that the FFT-Pronyspectral ratio technique can be implemented only when the time signal consists of a single wave mode, which explains the importance of achieving a clear isolation and resolution of the pseudo-Stoneley wave in the time domain by means of the acoustical funnel.…”