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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.
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 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]
5 5- Strong (強震) 80 gal and above 15–30 cm/s Most people are considerably frightened. Walls crack; heavy furniture may overturn. Noticeably felt by drivers; some chimneys and large archways topple over. 5+ 30–50 cm/s 6 6- Very strong (烈震) 50–80 cm/s People have trouble walking due to violent rocking.
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 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 ...