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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.
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.
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 United States Geological Survey developed an Instrumental Intensity scale, which maps peak ground acceleration and peak ground velocity on an intensity scale similar to the felt Mercalli scale. These values are used to create shake maps by seismologists around the world. [3]
The maximum Modified Mercalli intensity observed was XII. [ 15 ] The many more aftershocks include one magnitude 7 aftershock to the December 16, 1811, earthquake which occurred at 6:00 UTC (12:00 am local time) on December 17, 1811, and one magnitude 7 aftershock to the February 7, 1812, earthquake which occurred on the same day at 4:40 UTC ...
It was based on the experiences being available in the early 1960s from the application of the Modified Mercalli intensity scale and the 1953 version of the Medvedev scale, known also as the GEOFIAN scale. [1] With minor modifications in the mid-1970s and early 1980s, the MSK scale became widely used in Europe and the USSR.
Date/Time Thumbnail Dimensions User Comment; current: 21:45, 30 May 2006: 612 × 884 (539 KB): Andre315: Public Domain<br/> Intensity map for the 1906 San Francisco Earthquake deduced from the Lawson report<br/> from U.S. Geological Survey Open-File Report 2005-1135<br/> Modified Mercalli Intensity Maps for the 1906 San Francisco Earthquake Plotted in ShakeM
A strong ground motions map by the USGS. A maximum Modified Mercalli intensity of VIII (Severe) was estimated by the USGS. According to the USGS Prompt Assessment of Global Earthquakes for Response service, there was a 35 percent probability of shaking-related fatalities between 100 and 1,000. [20]