Rayleigh waves are the other type of surface wave. These are also called “ground rolls” in earthquakes and are similar to water waves. The difference between water waves and Rayleigh waves is that the particle oscillations in water waves move in a clockwise direction and the particles in the Rayleigh waves (solids) move in a counter-clockwise direction. As this wave moves through the solid surface of the Earth, the land moves up and down in the direction of the wave’s energy path. These waves are named after Lord Rayleigh who used math to predict the existence of this wave.