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The formula above made it much easier to estimate the energy-based magnitude M w , but it changed the fundamental nature of the scale into a moment magnitude scale. USGS seismologist Thomas C. Hanks noted that Kanamori's M w scale was very similar to a relationship between M L and M 0 that was reported by Thatcher & Hanks (1973)
Officially it's called the moment magnitude scale. It's a logarithmic scale, meaning each number is 10 times as strong as the one before it. So a 5.0 earthquake is ten times stronger than a 4.0.
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]
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. Earthquakes of magnitude 8.0 and greater from 1900 to 2018.
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]
Magnitude scales measure the inherent force or strength of an earthquake – an event occurring at greater or lesser depth. (The "M w" scale is widely used.) The MM scale measures intensity of shaking, at any particular location, on the surface. It was developed from Giuseppe Mercalli's Mercalli intensity scale of 1902.
Seismic moment is the basis of the moment magnitude scale introduced by Caltech's Thomas C. Hanks and Hiroo Kanamori, which is often used to compare the size of different earthquakes and is especially useful for comparing the sizes of large (great) earthquakes. The seismic moment is not restricted to earthquakes.
An important parameter in the calculation of seismic hazard, maximum magnitude (expressed as Moment magnitude scale) is also one of the more contentious.The choice of the value can greatly influence the final outcome of the results, yet this is most likely a size of earthquake that has not yet occurred in the region under study.