- Richter scale
a scale, ranging from 1 to 10, for indicating the intensity of an earthquake.[1935-40; after Charles F. Richter (1900-85), U.S. seismologist]
* * *Widely used measure of the magnitude of an earthquake, introduced in 1935 by U.S. seismologists Beno Gutenberg (1889–1960) and Charles F. Richter (1900–1985).The scale is logarithmic, so that each increase of one unit represents a 10-fold increase in magnitude (amplitude of seismic waves). The magnitude is then translated into energy released. Earthquakes that are fainter than the ones originally chosen to define magnitude zero are accommodated by using negative numbers. Though the scale has no theoretical upper limit, the most severe earthquakes have not exceeded a scale value of 9. The moment magnitude scale, in use since 1993, is more accurate for large earthquakes; it takes into account the amount of fault slippage, the size of the area ruptured, and the nature of the materials that faulted.
* * *Richter scale of earthquake magnitudewidely used quantitative measure of the magnitude of an earthquake, devised in 1935 by American seismologist Charles F. Richter (Richter, Charles F.). See table (Richter scale of earthquake magnitude).The Richter scale was originally devised to measure the magnitude of local earthquakes in southern California as recorded by a specific kind of seismograph. Current scientific practice has replaced the original Richter scale with other scales, including the body-wave magnitude scale and the moment magnitude scale, which have no restrictions regarding distance and type of seismograph used. Nevertheless, the Richter scale is still commonly cited in news reports of earthquake severity.On the original Richter scale the smallest earthquakes measurable at that time were assigned values close to zero. Since modern seismographs can detect seismic waves even smaller than those originally chosen for zero magnitude, the Richter scale now measures earthquakes having negative magnitudes. Each increase of one unit on the scale represents a 10-fold increase in the magnitude of an earthquake—in other words, numbers on the Richter scale are proportional to the common (base 10) logarithms of maximum wave amplitudes. In theory the scale has no upper limit, but in practice no earthquake has ever been registered above magnitude 9.
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