Том: 30 , Год издания: 2011

Numerical modeling was performed to find optimal variants of estimating complex-valued weaknesses responsible for velocity - attenuation anisotropy in an attenuative linear-slip transversely isotropic (LSTI) model of a fractured medium. Velocities and attenuations of the three wave types (qP, qSV, SH) versus the angle between the symmetry axis and the wave normal were computed for media with different values of the ratio Vs/Vp in the isotropic background and varying values of the real and imaginary parts of the normal and tangential weaknesses. These data were analyzed and then inverted for complexvalued weaknesses. Inversion was made for various combinations of data (velocities, attenuations), wave types and angle intervals (0°-45°, 45°-90°). The results concerning the optimal ways for estimation the complexvalued weaknesses occurred to be as follows. At first, the values of the real parts neglecting the unknown imaginary parts of the weaknesses are to be determined from the velocity anisotropy, namely, for the normal weakness using qP-wave and for the tangential one using SH-wave. Then with the values of the real parts known, one determines the values of the imaginary parts. For the normal weakness, the qP-wave attenuation anisotropy is used, and for the tangential one SH-wave anisotropy. The velocity and attenuation anisotropy of qSV-wave is recommended to use only in the case of weak anisotropy to avoid cusps at the qSV-wave ray velocity surface. Joint inversion of qP- and SH-wave data can also yield good results.