Translations:Dictionary:Transverse isotropy/5/en

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With a vertical symmetry axis, pure S- and P-waves may exist only in certain directions. SH-wavefronts are ellipsoidal in shape (elliptical anisotropy, q.v.; see Figure A-10c) and SV- and P-modes of propagation are coupled with wavefronts that in general are not orthogonal to the directions of wave propagation. Phase velocity is velocity perpendicular to a surface of constant phase (wavefront) and ray velocity (in the direction of energy transport, also called group velocity) is generally not in the same direction as phase velocity, phase and ray velocities being different (see Figure A-14a). The reciprocal of phase velocity, also a vector quantity, is called slowness. The surfaces for SV-wavefronts may have cusps.