Flexi Says: Sediments that are saturated with water undergo liquefaction and become like quicksand. Soil on a hillside may become a landslide. Surface waves are the slowest of all seismic waves found to be linked with liquefication. They travel at 2.5 km (1.5 miles) per second. There are two types of surface waves. Love waves move side-to-side, much like a snake. Rayleigh waves produce a rolling motion as they move up and backward.