PARTICLE MOTION OF PLANE WAVES IN VISCOELASTIC ANISOTROPIC MEDIA

Particle motion of homogeneous and inhomogeneous time-harmonic plane waves propagat-ing in unbounded viscoelastic anisotropic media is generally elliptical. Exception is linear polarization of P and S waves propagating along some specific directions. A typical example is a linear polarization of SH waves propagating in a plane of symmetry of a viscoelastic anisotropic medium. Two most important characteristics of the particle motion are the orientation of the axes of the polarization ellipse and its eccentricity. They both usually vary considerably with the direction of wavefront propagation, and with varying strength of inhomogeneity of the considered plane wave. The orientation of the P-wave polarization ellipse generally differs from the direction of wavefront propagation, and it is usually closer to the direction of the energy flux. The orientation of the polarization ellipses of S waves often differs from the direction perpendicular to the wavefront propagation, and it is usually closer to the direction perpendicular to the direction of the energy flux. The eccentricity of the polarization ellipse depends particularly strongly on the inhomogeneity of the plane wave. For homogeneous plane waves, the particle motion is usually nearly linear, i.e., polarization ellipses have large eccentricity, and the eccentricity decreases with increasing inhomogeneity of the wave. For strongly inhomogeneous plane waves, the polarization ellipse becomes nearly circular, eccentricity being very small. The eccentricity of the polarization ellipse usually also decreases in the vicinity of singular directions. Viscoelastic anisotropic medium, polarization, homogeneous and inhomogeneous plane wave