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Alternating
transverse motions (perpendicular to the direction of propagation, and the
ray path); commonly approximately polarized such that particle motion is in
vertical or horizontal planes.
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VS
~ 3 – 4 km/s in typical Earth’s crust; >~ 4.5 km/s in Earth’s mantle; ~ 2.5-3.0 km/s in (solid) inner core.
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S-waves
do not travel through fluids, so do not exist in Earth’s outer core
(inferred to be primarily liquid iron) or in air or water or molten rock
(magma). S waves travel slower than P waves in a solid and,
therefore, arrive after the P wave.
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