Approximate expressions for viscous attenuation in marine sediments: relating Biot's "critical" and "peak" frequencies.

Abstract

Simple approximate relations are proposed for the viscous attenuation per cycle of the fast compressional and shear waves in the low-to-intermediate frequency range. Corresponding closed-form formulas are derived for frequencies at which maximum viscous attenuation per cycle occurs according to the Biot-Stoll theory of elastic wave propagation in marine sediments. In the new formulas, Biot's approximation [M. A. Biot, J. Acoust. Soc. Am. 34, 1254-1264 (1962)] for the frequency-dependent viscosity correction factor F(f) and the assumption of relatively low specific loss (Q(-1)<(0.2) [J. Geertsma and D. C. Smith, Geophysics 26(2), 169-181 (1962)] are used to provide an accurate representation of the fast compressional and shear wave attenuation from low frequencies through a transition region extending to two or three times Biot's critical frequency f(c). The approximate viscodynamic behavior of marine sediments for the fast compressional and shear waves shows similarities to that of a "homogeneous relaxation" process for an anelastic linear element [A. M. Freudenthal and H. Geiringer, Encyclopedia of Physics (Springer-Verlag. 1958), Vol. 6].