Retrograde elliptical particle motion at a free elastic surface
Rayleigh waves travel along a free surface with speed c_R ≈ c_s(0.862 + 1.14ν)/(1 + ν). Particle trajectories are retrograde ellipses: horizontal motion leads vertical by 90°. Amplitude decays exponentially with depth ∝ e^{−κz}, confining energy to roughly one wavelength depth. They carry ~2/3 of seismic energy from shallow earthquakes.