Degeneracies of the slowness surfaces of quasi shear (and quasi compressional) waves in low-symmetry anisotropic media (such as orthorhombic), known as point singularities, pose difficulties during modeling and inversion, but can be potentially used in the latter as model parameters constraints. We analyze the relation between anisotropy strength and the number and distribution of singularities in orthorhombic media. Numerical experiments demonstrate that in weakly anisotropic media, only three patterns of the singularity locations are allowed, and it is impossible to encounter models with zero or maximum number of singularities unless shear stiffnesses are larger than compressional stiffnesses. Depending on the anisotropy strength, the off-plane singularities follow closed and non-intersecting trajectories.


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  1. Alshits, V. and Lothe, J.
    [1979] Elastic waves in triclinic crystals. II. Topology of polarization fields and some general theorems. Soviet Physics, Crystallography, 24, 393–398. Originally in Russian, 1978, Crystallography, 24, 683–693.
    [Google Scholar]
  2. Boulanger, P. and Hayes, M.
    [1998] Acoustic axes for elastic waves in crystals: theory and applications. Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 454, 2323–2346.
    [Google Scholar]
  3. Grechka, V.
    [2015] Shear-wave group-velocity surfaces in low-symmetry anisotropic media. Geophysics, 80(1), C1–C7.
    [Google Scholar]
  4. Grechka, V. and Yaskevich, S.
    [2014] Azimuthal anisotropy in microseismic monitoring: A Bakken case study. Geophysics, 79(1), KS1–KS12.
    [Google Scholar]
  5. Ivanov, Y. and Stovas, A.
    [2017] S-wave singularities in tilted orthorhombic media. Geophysics, 82(4), WA11–WA21.
    [Google Scholar]
  6. Khatkevich, A.G.
    [1977] Classification of crystals by acoustic properties. Soviet Physics, Crystallography, 22, 701–705.
    [Google Scholar]
  7. Musgrave, M.J.P.
    [1985] Acoustic Axes in Orthorhombic Media. Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 401(1820), 131–143.
    [Google Scholar]
  8. Ranganathan, S.I. and Ostoja-Starzewski, M.
    [2008] Universal Elastic Anisotropy Index. Physical Review Letters, 101(5), 055504.
    [Google Scholar]
  9. Vavryčuk, V.
    [2003] Behavior of rays near singularities in anisotropic media. Physical Review B, 67(5), 054105.
    [Google Scholar]
  10. [2005] Acoustic axes in triclinic anisotropy. The Journal of the Acoustical Society of America, 118(2), 647–653.
    [Google Scholar]
  11. Vavrycuk, V.
    [2013] Inversion for weak triclinic anisotropy from acoustic axes. Wave Motion, 50(8), 1271–1282.
    [Google Scholar]

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