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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]
The first scale for measuring earthquake magnitudes, developed in 1935 by Charles F. Richter and popularly known as the "Richter" scale, is actually the local magnitude scale, label ML or M L. [11] Richter established two features now common to all magnitude scales.
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).
By this time, scientists were well aware of the threat, but seismology was still in its infancy. Following destructive earthquakes in the late 19th and early 20th centuries, real estate developers , press , and boosters minimized and downplayed the risk of earthquakes out of fear that the ongoing economic boom would be negatively affected.
In southern California about 6% of M≥3.0 earthquakes are "followed by an earthquake of larger magnitude within 5 days and 10 km." [12] In central Italy 9.5% of M≥3.0 earthquakes are followed by a larger event within 48 hours and 30 km. [13] While such statistics are not satisfactory for purposes of prediction (giving ten to twenty false ...
The 1906 earthquake preceded the development of the Richter scale by three decades. The most widely accepted estimate for the magnitude of the quake on the modern moment magnitude scale is 7.9; [ 1 ] values from 7.7 to as high as 8.3 have been proposed. [ 8 ]
It is therefore too short to reliably measure the M of an earthquake rupture exceeding 100 km. In these cases, an in depth analysis, which takes time, is needed to arrive at the correct M. As an example, the Wenchuan earthquake of 12 May 2008 had originally been assigned M7.5 in real-time. Later estimates were M7.9 to M8.0.
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 ...