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v. t. e. 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 " Mw ...
In 1902, Italian seismologist Giuseppe Mercalli, created the Mercalli Scale, a new 12-grade scale. Significant improvements were achieved, mainly by Charles Francis Richter during the 1950s, when (1) a correlation was found between seismic intensity and the Peak ground acceleration (PGA; see the equation that Richter found for California).
AD 62 Pompeii earthquake. On 5 February AD 62, an earthquake of an estimated magnitude of between 5 and 6 and a maximum intensity of IX or X on the Mercalli scale struck the towns of Pompeii and Herculaneum, severely damaging them. The earthquake may have been a precursor to the eruption of Mount Vesuvius in AD 79, which destroyed the same two ...
The sequence of events in 1759 began on October 30, with the smaller of the two severe main shocks that year, causing the deaths of 2000 people in Safed and other settlements. This initial event was estimated at 6.6 on the surface wave magnitude scale and given a rating of VIII (Severe) to IX (Violent) on the Mercalli intensity scale. [5]
Richter established two features now common to all magnitude scales. First, the scale is logarithmic, so that each unit represents a ten-fold increase in the amplitude of the seismic waves. [ 12 ] As the energy of a wave is proportional to A 1.5 , where A denotes the amplitude, each unit of magnitude represents a 10 1.5 ≈32-fold increase in ...
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.
A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected. The relative motion between the weight (called the mass) and the frame provides a measurement of the vertical ground motion. A rotating drum is attached to the frame and ...
Testers ranked each may on a scale of 1 to 5, with 1 being the lowest and 5 being the highest, and we tallied the rankings to determine the winning brands. The Contenders Duke's Real Smooth ...