Editing Seismic wave (section)

==== Rayleigh waves ====
{{Main|Rayleigh wave}} 
Rayleigh waves, also called ground roll, are surface waves that propagate with motions that are similar to those of waves on the surface of water (note, however, that the associated seismic particle motion at shallow depths is typically retrograde, and that the restoring force in Rayleigh and in other seismic waves is elastic, not gravitational as for water waves). The existence of these waves was predicted by John William Strutt, [[Lord Rayleigh]], in 1885.<ref>{{cite journal |last1=Rayleigh |first1=Lord |title=On waves propagated along the plane surface of an elastic solid |journal=Proceedings of the London Mathematical Society |date=1885 |volume=17 |pages=4–11 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.$b671850&view=1up&seq=11}}</ref> They are slower than body waves, e.g., at roughly 90% of the velocity of S waves for typical homogeneous elastic media. In a layered medium (e.g., the crust and [[upper mantle (Earth)|upper mantle]]) the velocity of the Rayleigh waves depends on their frequency and wavelength. See also [[Lamb waves]].