Surface waves, i.e. Rayleigh waves and Love waves, propagate along the Earth´s surface from their sources, usually large earthquakes. They possess the remarkable property of dispersion. Waves of different frequency propagate with different velocity. The dispersion depends on the velocity structure of the crust and the underlying layers. The velocity structure can be derived by measuring the velocity of the different wavelengths of the surface waves.
Recent publications of the Institute of Earth Sciences on this topic:
Bjarnason, I. Th. & Schmeling, H. (2009). The lithosphere and asthenosphere of the Iceland hotspot from surface waves. Geophysical Journal International, (178), 394-418. DOI: 10.1111/j.1365-246X.2009.04155.x