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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 first widely adopted intensity scale, the 10-grade Rossi–Forel scale, was introduced in the late 19th century. [8] In 1902, Italian seismologist Giuseppe Mercalli , created the Mercalli Scale, a new 12-grade scale.
The second, now known as the Mercalli intensity scale, had ten degrees, and elaborated the descriptions in the Rossi–Forel scale. [4] The Mercalli intensity scale is, in modified form, still used. [5] Unlike the Richter scale, which measures the energy released by an earthquake, the Mercalli intensity scale measures the effects of an
The old Modified Mercalli intensity scale (MM), a relic of the pre-instrument days, remains useful in the sense that each intensity-level provides an observable difference in seismic damage. After many years of trying every possible manipulation of accelerometer-time histories, it turns out that the extremely simple peak ground velocity (PGV ...
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. [4] [5]
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The 1979 Saint Elias earthquake affected Alaska at 12:27 AKST on 28 February. The thrust-faulting M w 7.5 earthquake had an epicenter in the Granite Mountains.Though the maximum recorded Modified Mercalli intensity was VII (Very strong), damage was minimal and there were no casualties due to the remoteness of the faulting.
UTC time: 1939-12-26 23:57:23: ISC event: 902291: USGS-ANSSComCat: Local date: 27 December 1939 (): Local time: 1:57:23 a.m. Magnitude: 7.8 M w [1]: Depth: 20 km (12 mi) [1] Epicenter: 1]: Fault: North Anatolian Fault: Type: Strike-slip: Areas affected: Erzincan Province Turkey: Total damage: 116,720 buildings were seriously damaged: Max. intensity: MMI XII (Extreme) [2]: Tsunami: 0.53 m (1 ft ...