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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]
Second, Richter arbitrarily defined the zero point of the scale to be where an earthquake at a distance of 100 km makes a maximum horizontal displacement of 0.001 millimeters (1 μm, or 0.00004 in.) on a seismogram recorded with a Wood-Anderson torsion seismograph. [14]
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 ...
Alternatively, a b-value significantly different from 1.0 may suggest a problem with the data set; e.g. it is incomplete or contains errors in calculating magnitude. Roll-off compared to ideal GR law with b=1 Magnitude of the August 2016 Central Italy earthquake (red dot) and aftershocks (which continued to occur after the period shown here)
Two scales were developed, one based on surface waves, , and one on body waves, . Surface waves with a period near 20 s generally produce the largest amplitudes on a standard long-period seismograph, and so the amplitude of these waves is used to determine M s {\displaystyle M_{s}} , using an equation similar to that used for M L {\displaystyle ...
A pie chart comparing the seismic moment release of the three largest earthquakes for the hundred-year period from 1906 to 2005 with that for all earthquakes of magnitudes <6, 6 to 7, 7 to 8, and >8 for the same period. The 2011 Japan quake would be roughly similar to Sumatra.
Stover & Coffman 1993 uses various seismic scales. M la is a local magnitude that is equivalent to M L (Richter magnitude scale) and is used for events that occurred prior to the instrumental period. It is based on the area of perceptibility (as presented on isoseismal maps). M w = moment magnitude scale and M s = surface wave magnitude
In 1902, Italian seismologist Giuseppe Mercalli, created the Mercalli Scale, a new 12-grade scale. Significant improvements were achieved, mainly by Charles Francis Richter during the 1950s, when (1) a correlation was found between seismic intensity and the Peak ground acceleration (PGA; see the equation that Richter found for California).