Wet, soft or sandy soils can behave like a liquid when they are shaken during an earthquake. When this happens the soil loses all its strength and cannot support any weight. Objects sitting on the surface of the soil just sink into it.

Next time you are on a beach, try your own experiment with liquefaction. Stand on some hard wet sand just by the sea. Then, with your feet in one position, rock backwards and forwards. Fairly soon, you will notice that the sand around your feet is acting like a liquid, and that your feet are sinking into the sand.

See some videos demonstrating liquefaction using a model building sitting on a sandy soil. An earthquake simulator was used to shake the model and the sand.

Video 1 - Building tilting as sand liquefies - Download (195Kb) or view on-line.
Video 2 - Close up of sand liquefying - Download (132Kb) or view on-line

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