The 3*3*3*3 frequency-domain stiffness tensor is complex–valued in viscoelastic media. The 3*3 Christoffel matrix is then also complex-valued. We study the properties of the real and imaginary parts of its complex-valued eigenvectors with emphasis on their behaviour at S-wave singularities. We also approximate the complex-valued eigenvectors of the Christoffel matrix by the reference real-valued polarization vectors, which may be required by some computer codes.
Attenuation, anisotropy, wave propagation, ray theory, Christoffel matrix, polarization
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