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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).
Even for distant earthquakes, measuring the duration of the shaking (as well as the amplitude) provides a better measure of the earthquake's total energy. Measurement of duration is incorporated in some modern scales, such as M wpd and mB c . [66] M c scales usually measure the duration or amplitude of a part of the seismic wave, the coda. [67]
1960 Valdivia earthquake. The 1960 Valdivia earthquake and tsunami (Spanish: Terremoto de Valdivia) or the Great Chilean earthquake (Gran terremoto de Chile) on 22 May 1960 was the most powerful earthquake ever recorded. Most studies have placed it at 9.4–9.6 on the moment magnitude scale, [ 1 ] while some studies have placed the magnitude ...
The intraplate earthquake measured 7.6 on the moment magnitude scale and occurred at 17.4 km (10.8 mi) depth. [1] It had a maximum felt intensity of X (Extreme) on the Mercalli intensity scale. The earthquake killed at least 20,023 people (including 19 in southeastern Pakistan), injured another 166,000 and destroyed nearly over 400,000 buildings.
Peak ground acceleration can be expressed in fractions of g (the standard acceleration due to Earth's gravity, equivalent to g-force) as either a decimal or percentage; in m/s 2 (1 g = 9.81 m/s 2); [7] or in multiples of Gal, where 1 Gal is equal to 0.01 m/s 2 (1 g = 981 Gal).
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 ...
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 ...