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The moment magnitude scale (MMS; denoted explicitly with M w or Mwg, and generally implied with use of a single M for magnitude [1]) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment.
An earthquake's seismic moment can be estimated in various ways, which are the bases of the M wb, M wr, M wc, M ww, M wp, M i, and M wpd scales, all subtypes of the generic M w scale. See Moment magnitude scale § Subtypes for details. Seismic moment is considered the most objective measure of an earthquake's "size" in regard of total energy. [50]
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.
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 ...
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]
Seismic magnitude scales, the energy in an earthquake, measures include: Moment magnitude scale, based on seismic moment, supersedes the Richter scale; Richter magnitude scale, the energy of an earthquake, superseded by Moment scale; Surface-wave magnitude, based on Rayleigh surface wave measurement through heat conduction
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 ...
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. [3]