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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]
Much of an earthquake's total energy as measured by M w is dissipated as friction (resulting in heating of the crust). [52] An earthquake's potential to cause strong ground shaking depends on the comparatively small fraction of energy radiated as seismic waves, and is better measured on the energy magnitude scale, M e. [53]
This meant that giant earthquakes such as the 1960 Chilean earthquake (M 9.5) were only assigned an M s 8.2. Caltech seismologist Hiroo Kanamori [ 47 ] recognized this deficiency and took the simple but important step of defining a magnitude based on estimates of radiated energy, M w , where the "w" stood for work (energy):
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 ...
Differences in the crust underlying North America east of the Rocky Mountains makes that area more sensitive to earthquakes. Shown here: the 1895 New Madrid earthquake, M ~6, was felt through most of the central U.S., while the 1994 Northridge quake, though almost ten times stronger at M 6.7, was felt only in southern California. From USGS Fact ...
The 2008 Reno earthquakes, also known as the "Mogul-Somersett earthquake sequence", occurred in or near the western Reno, Nevada, suburbs of Mogul and Somersett. The earthquake swarm began in February 2008, but the first significant quake of the series occurred on April 15, 2008, registering a 3.6 magnitude. On April 24, 2008, two quakes in the ...
This type of strong-motion seismometer recorded upon a smoked glass (glass with carbon soot). While not sensitive enough to detect distant earthquakes, this instrument could indicate the direction of the pressure waves and thus help find the epicenter of a local quake. Such instruments were useful in the analysis of the 1906 San Francisco ...
The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in Southern California. The unanticipated thrust earthquake had a magnitude of 6.5 on the M s scale and 6.6 on the M w scale, and a maximum Mercalli intensity of XI ( Extreme ).