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At 05:12 AM Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (Extreme).
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]
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]
On April 18, 1906, San Franciscans were awoken at 5:11 a.m. by what would become the deadliest earthquake in U.S. history.
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. M w was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori.
Magnitude is a measurement of the strength of an earthquake. Officially it's called the moment magnitude scale . It's a logarithmic scale , meaning each number is 10 times as strong as the one ...
Early developments at the Caltech lab included an earthquake observation network using their own custom-built short-period seismometers, the Richter scale, and the Modified Mercalli intensity scale (an updated version of the Mercalli intensity scale). In 1933, the Long Beach earthquake occurred in a populated area and damaged or destroyed many ...
There was a magnitude 4.6 earthquake on Feb. 9, strong enough to toss items off a counter; and a magnitude 4.7 on Sept. 12 — startling enough that the city's mayor and his wife dove under their ...