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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]
First, the scale is logarithmic, so that each unit represents a ten-fold increase in the amplitude of the seismic waves. [12] As the energy of a wave is proportional to A 1.5, where A denotes the amplitude, each unit of magnitude represents a 10 1.5 ≈ 32-fold increase in the seismic energy (strength) of an earthquake. [13]
Thus, a magnitude zero microearthquake has a seismic moment of approximately 1.1 × 10 9 N⋅m, while the Great Chilean earthquake of 1960, with an estimated moment magnitude of 9.4–9.6, had a seismic moment between 1.4 × 10 23 N⋅m and 2.8 × 10 23 N⋅m. Seismic moment magnitude (M wg or Das Magnitude Scale ) and moment magnitude (M w) scales
Gutenberg–Richter law fitted to the aftershocks of the August 2016 Central Italy earthquake, during the Aug 22 – Sep 1 period. Notice that the linear fit fails at the upper and lower end, due to lack of registered events. Since the recording period is only 10 days, events of magnitude greater than 6 has not yet appeared.
Seismic intensity scales categorize the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake.They are distinguished from seismic magnitude scales, which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking.
[7] [8] These values vary in different earthquakes, and in differing sites within one earthquake event, depending on a number of factors. These include the length of the fault, magnitude, the depth of the quake, the distance from the epicentre, the duration (length of the shake cycle), and the geology of the ground (subsurface).
The formula to calculate surface wave magnitude is: [3] = + (), where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s (usually 20 ± 2 seconds), Δ is the epicentral distance in °, and
Charles Francis Richter (/ ˈ r ɪ k t ər /; April 26, 1900 – September 30, 1985) was an American seismologist and physicist.He is the namesake and one of the creators of the Richter scale, which, until the development of the moment magnitude scale in 1979, was widely used to quantify the size of earthquakes.