2023/01/05 by Qi Hao, Ilya Tsvankin, Hao, Qi +1
Earth and Planetary Sciences · Engineering · #FOS: Physical sciences #Geophysical Methods and Applications #Geophysics (physics.geo-ph) #Seismic Imaging and Inversion Techniques #Seismic Waves and Analysis
paper · pdf · doi:10.48550/arxiv.2301.01939
openalex publication_date 2023/01/05 · openalex created_date 2023/01/08 · openalex updated_date 2026/07/28
Transversely isotropic (TI) media with the frequency-independent quality-factor elements (also called ``constant-Q'' transverse isotropy) are often used to describe attenuation anisotropy in sedimentary rocks. The attenuation coefficients in constant-Q 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-Q media are frequency-independent. Here, we present concise analytic formulae for the Thomsen-type attenuation parameters for Kjartansson's constant-Q TI model and show that one of them (δQ) varies with frequency. The analytic expression for δQ helps evaluate the frequency dependence of the normalized attenuation coefficients of P- and SV-waves by introducing the newly defined ``dispersion factors''. Viscoacoustic constant-Q transverse isotropy is also discussed as a special case, for which the elliptical condition and simplified expressions for the parameters δ and δQ are derived. Our results show that in the presence of significant absorption the attenuation coefficients of the ``constant-Q'' 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.