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The Richter scale [1] (/ ˈ r ɪ k t ər /), also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, [2] is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and presented in Richter's landmark 1935 paper, where he called it the "magnitude scale". [3]
Even for distant earthquakes, measuring the duration of the shaking (as well as the amplitude) provides a better measure of the earthquake's total energy. Measurement of duration is incorporated in some modern scales, such as M wpd and mB c . [66] M c scales usually measure the duration or amplitude of a part of the seismic wave, the coda. [67]
This magnitude scale is related to the local magnitude scale proposed by Charles Francis Richter in 1935, with modifications from both Richter and Beno Gutenberg throughout the 1940s and 1950s. [ 1 ] [ 2 ] It is currently used in People's Republic of China as a national standard ( GB 17740-1999 ) for categorising earthquakes.
Seismic intensity scales categorize the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake. They are distinguished from seismic magnitude scales , which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking.
Early USGS/NEIC practice was to measure mb on the first second (just the first few P-waves [9]), but since 1978 they measure the first twenty seconds. [10] The modern practice is to measure short-period mb scale at less than three seconds, while the broadband mB BB scale is measured at periods of up to 30 seconds. [11]
The Kelly Kiloton Index (KKI) was invented by H. A. Kelly of University of California, Los Angeles in 2006 as an alternative to the logarithmic Richter scale (which dates to 1935). Its unit of measurement is the metric kiloton of TNT, which yields a practical measurement of the seismic movement of force which is more understandable by the lay ...
The Modified Mercalli intensity scale (MM, MMI, or MCS) measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. Magnitude scales measure the inherent force or strength of an earthquake – an event occurring at greater or lesser depth. (The "M w" scale is ...
Seismic moment is the basis of the moment magnitude scale introduced by Caltech's Thomas C. Hanks and Hiroo Kanamori, which is often used to compare the size of different earthquakes and is especially useful for comparing the sizes of large (great) earthquakes. The seismic moment is not restricted to earthquakes.