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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 intensity and death toll depend on several factors (earthquake depth, epicenter location, and population density, to name a few) and can vary widely. Millions of minor earthquakes occur every year worldwide, equating to hundreds every hour every day. [15] On the other hand, earthquakes of magnitude ≥8.0 occur about once a year, on average ...
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.
Earthquake intensity is a slightly different number that measures people's on-the-ground descriptions. It explains the severity of the temblor's shaking and its effects on people and the ...
The intensity of local ground-shaking depends on several factors besides the magnitude of the earthquake, [3] one of the most important being soil conditions. For instance, thick layers of soft soil (such as fill) can amplify seismic waves, often at a considerable distance from the source, while sedimentary basins will often resonate ...
The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on the distance from the earthquake and the underlying rock or soil makeup. [56]
PGA is an important parameter (also known as an intensity measure) for earthquake engineering, The design basis earthquake ground motion (DBEGM) [2] is often defined in terms of PGA. Unlike the Richter and moment magnitude scales, it is not a measure of the total energy (magnitude, or size) of an earthquake, but rather of how much the earth ...
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]