No two earthquakes are exactly alike. During an earthquake, the ground does not move just back-and-forth or up-and-down, but may react in an undulating wave, a brief sharp shake, or as a tremor that builds and recedes. The strength of an earthquake varies as well, depending on the amount of stress to be released and if it starts deep in the earth's crust or closer to the surface.
A shake table is designed to recreate both the movements of the ground and the varied forces generated by earthquakes. It is an invaluable testing tool for the simulation of earthquakes in a laboratory. A shake table typically has five degrees of freedom, meaning it can move in five separate directions. The table can move horizontally and vertically, roll back and forth, rock from side to side, and twist on a central axis.
A computer system controls the motion of the table. This allows researchers to select from more than one thousand earthquake records in order to simulate the vibrations of actual past earthquakes. Researchers can "create their own" earthquakes as well, including levels beyond the Richter scale.
University of Buffalo, SUNY
The two Earthquake Simulators, known also as Shake Tables at the University of Buffalo, SUNY may be moved up to 100 feet apart. Further details on the shake tables and the facility are available from the links below.
University of California, San Diego
The University of California at San Diego boasts the largest outdoor shake table in the U.S. At 25 by 40 ft, the world's first outdoor shake table is also the largest shake table in the U.S. - able to test structures weighing up to 2,200 tons and as tall as 100 ft. Its hydraulic actuators are capable of shaking at speeds up to 6 fps allowing it to create simulations of the most devastating earthquakes ever recorded.
University of Nevada, Reno
The NEES Equipment Site at the University of Nevada, Reno is a biaxial, multiple shake table facility (with three identical biaxial shake tables - which can function in unison or independently) that is suitable for conducting of research on long, spatially distributed, structural and geotechnical systems.