The standard modern measure of earthquake size, computed from seismic moment, the product of fault area, slip and rock rigidity, rather than from the amplitude a particular instrument records. Unlike the Richter scale it does not saturate for great earthquakes, which is why the largest events, like the magnitude 9 class megathrusts of 2004 and 2011, are stated in moment magnitude. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Facts
Origin YearIntroduced by Thomas Hanks and Hiroo Kanamori in 1979, building on Kanamori's 1977 work on seismic moment. Connections
Anticipated By
Richter's local magnitude is the scale moment magnitude was designed to be consistent with while fixing its saturation for great earthquakes.
Source Moment Magnitude Scale (Wikipedia)
Associated With
Modern seismology pairs Mercalli intensity readings with moment magnitude for the same reason it once paired them with Richter: intensity is local and felt, magnitude is a single value for the whole earthquake.
Source Modified Mercalli Intensity Scale (Wikipedia)
In Discipline
Source Moment Magnitude Scale (Wikipedia)
Sources
1. Moment Magnitude Scale (Wikipedia)
Wikimedia FoundationLead sectionQuote, Lead section
The moment magnitude scale (MMS; denoted explicitly with Mw or Mwg and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment.
Modified Mercalli Intensity Scale (Wikipedia)
Wikimedia FoundationAssociated With: Modified Mercalli Intensity ScaleView the Source Reader Challenges (0)
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