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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 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. [57]
The Richter scale [1] (/ ˈ r ɪ k t ər /), also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, [2] is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and presented in Richter's landmark 1935 paper, where he called it the "magnitude scale". [3]
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 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.
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 ...
At the beginning of the twentieth century, very little was known about how earthquakes happen, how seismic waves are generated and propagate through the Earth's crust, and what information they carry about the earthquake rupture process; the first magnitude scales were therefore empirical. [5]
A major earthquake measuring 7.4 hit Taiwan early Wednesday, killing 9 and injuring at least 1,000. A 7.4 earthquake is exponentially more destructive than the 4.8 quake that struck central New ...