Theory and laboratory experiment on anisotropy of attenuation and velocity in fractured medium. Part II* – Attenuation anisotropy

Abstract

The aim of this work consists in studying of anisotropy of attenuation linked to the velocity anisotropy in fractured media which are transversely isotropic (TI) due to aligned fractures. We develop a theory that predicts certain relationship between anisotropies of P-, SH- and SV-wave attenuation and velocity. Taking into account the interplay of velocities and attenuations, we develop the effective TI model of attenuative fractured medium fitted to the experimental data. In the first part*, we consider anisotropy of velocity, and in the second part, which is this paper, - anisotropy of attenuation. We perform joint inversion of the data on attenuation and velocity of P, SV-, and SH-waves taking into account their interrelationship due to the mutual dependence on the complex weaknesses – the normal and the tangential ones. We try to verify the proposed theoretical model by means of comparing it with the experimental data. We found out that Thomsen-style attenuation parameter is independent of attenuation associated with cracks; it is a simple function of -ratio in model material. The attenuation parameter εQ is independent of attenuation associated with cracks; it is a simple function of VP/VS-ratio in model material. The attenuation parameter δQ may be meaningful for fracture characterization because it is defined by the QP/QS-ratio.