Richter scale

Richter scale, scale devised by C.F. Richter (1900–85), used to measure the magnitudes of earthquakes in terms of the amplitude and frequency of the surface waves. The largest recorded earthquakes are about 8.5. A great earthquake of magnitude 8 occurs only once every 5–10 years. An increase of one unit corresponds to a tenfold increase in the size of an earthquake.

See also: Earthquake; Seismograph.