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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 ...
That gave the Mercalli Scale, as well as the European MSK-64 scale that followed, a quantitative element representing the vulnerability of the building's type. [10] Since then, that scale has been called the Modified Mercalli intensity scale (MMS) and the evaluations of the seismic intensities are more reliable.
The first, six-level intensity scale was proposed by Egen in 1828 for an earthquake in Rhineland. [ 4 ] [ 5 ] Robert Mallet coined the term "isoseismal" and produced a map for the 1857 Basilicata earthquake with a three-fold intensity scale and used this and other information to identify the epicentral area (a term he also coined). [ 6 ]
The Mercalli intensity scale uses personal reports and observations to measure earthquake intensity but PGA is measured by instruments, such as accelerographs. It can be correlated to macroseismic intensities on the Mercalli scale [ 3 ] but these correlations are associated with large uncertainty.
Maximum intensities are indicated on the Modified Mercalli intensity scale and are sourced from United States Geological Survey (USGS) ShakeMap data. For the second consecutive year, activity was well below average, with only nine major quakes, it was also the first year since 2016 with no magnitude 8.0+ earthquakes.
The magnitude/intensity comparison table in the Mercalli intensity scale#Modified Mercalli Intensity scale section makes it appear as though magnitude and intensity are directly comparable, when in reality, the magnitude (number) necessary for a certain intensity is frequently lower than the intensity (number) of the shaking it produces. An ...
The magnitude 4.7 earthquake just north of Malibu on Thursday morning adds to what scientists say is an unusually active year for moderate earthquakes in Southern California.
The Japan Meteorological Agency said it recorded a maximum seismic intensity of 7 (Shindo 7), the highest level on its seismic intensity scale, [49] the first time that an earthquake of that intensity had been observed in the country since 2018. [50] [51] It corresponded to a maximum Modified Mercalli intensity of X–XI (Extreme). [15]