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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]
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.
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.
Richter's original scale, explicitly denoted with the symbol "ML" or "M L" (where "L" indicates "Local"), was developed for measuring the magnitude of earthquakes in the vicinity of southern California. While the "Richter" and moment magnitude scales are similar, they do differ, particularly for earthquakes stronger than about M 6.5, or deeper ...
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 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 ...
In two most recent investigations using statistically stable samples for Italian earthquakes (approximately 100,000 events over the period 1981–2002 in the Richter local [M L ] magnitude range of 3.5–5.8) [5] and for Indian earthquakes exemplified by an aftershock sequence of 121 events with M s (surface wave magnitude) > 4.0 in 2001 in the Bhuj area of northwestern India, [4] the latest ...