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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 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
However, this earlier scale did not include the subdivisions of intensity levels 5 and 6 into "upper" and "lower" categories, which had been introduced later in Japan. [52] In South Korea, a seismic intensity scale modeled after Japan’s was used in the past, but since 2001, the country has switched to the Modified Mercalli intensity scale. [53]
Modified Mercalli intensity scale; P. PHIVOLCS earthquake intensity scale; R. Rossi–Forel scale This page was last edited on 7 June 2023, at 16:38 (UTC). Text is ...
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 ...
Seismic Intensity Scale [1] [2] [3] Intensity Level (震度分級) Strong Ground Acceleration (cm/s 2,gal) Ground Speed (cm/s) What People Feel Effects Indoors Effects Outdoors; 0 Undetectable (無感) below 0.8 gal Imperceptible to humans 1 Slight (微震) 0.8-2.5 gal People may feel slight shaking when motionless 2 Weak (輕震) 2.5-8.0 gal