Thomsen-type parameters and attenuation coefficients for constant-Q transverse isotropy

Abstract

Transversely isotropic (TI) media with the frequency-independent quality-factor elements (also called ``constant-QQ'' transverse isotropy) are often used to describe attenuation anisotropy in sedimentary rocks. The attenuation coefficients in constant-QQ TI models can be conveniently defined in terms of the Thomsen-type attenuation-anisotropy parameters. Recent research indicates that not all those parameters for such constant-QQ media are frequency-independent. Here, we present concise analytic formulae for the Thomsen-type attenuation parameters for Kjartansson's constant-QQ TI model and show that one of them (δQ\delta_{Q}) varies with frequency. The analytic expression for δQ\delta_{Q} helps evaluate the frequency dependence of the normalized attenuation coefficients of P- and SV-waves by introducing the newly defined ``dispersion factors''. Viscoacoustic constant-QQ transverse isotropy is also discussed as a special case, for which the elliptical condition and simplified expressions for the parameters δ\delta and δQ\delta_{Q} are derived. Our results show that in the presence of significant absorption the attenuation coefficients of the ``constant-QQ'' model vary with frequency for oblique propagation with respect to the symmetry axis. This variation needs to be taken into account when applying the spectral-ratio method and other attenuation-analysis techniques

    Similar works

    Full text

    thumbnail-image

    Available Versions