Rayleigh waves are surface seismic waves produced by the interaction of P- and SV-waves at a free surface. They produce retrograde (backward, relative to propagation direction) elliptical particle motion in the vertical plane, and travel at a characteristic velocity slightly slower than the shear (S) wave velocity of the medium.
Rayleigh waves cause particles at the surface to move in retrograde elliptical orbits — moving opposite to the wave's direction of propagation at the top...
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