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