Abstrakt
We study behavior of attenuation (inhomogeneity) angles gamma, i.e.,angles between real and imaginary parts of the slowness vectors of inhomogeneous plane waves propagating in isotropic or anisotropic, perfectly elastic or viscoelastic, unbounded media. The angle gamma never exceeds the boundary attenuation angle c gamma*.
In isotropic viscoelastic media gamma* = 90(degrees); in anisotropic viscoelastic media c gamma* may be greater than, equal to, or less than 90 degrees. Plane waves with gamma } gamma* do not exist.
Because gamma* in anisotropic viscoelastic media is usually not known a priori, the commonly used specification of an inhomogeneous plane wave by the attenuation angle gamma may lead to serious problems. If gamma is chosen close to c gamma* or even larger, indeterminate, unstable or even nonphysical results are obtained.
We study properties of gamma* and show that the approach based on the mixed specification of the slowness vector fully avoids the problems mentioned above.