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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 ...
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.
Intensity 7 (震度7, Shindo-nana) is the highest level on the JMA seismic intensity scale, applied to earthquakes with an instrumental intensity (計測震度) of 6.5 or higher. [6] At Intensity 7, movement becomes nearly impossible without external support. [11] The intensity was created following the 1948 Fukui earthquake.
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 shakes at a given geographic point. The Mercalli intensity scale uses personal reports and observations to measure earthquake intensity but PGA is measured by instruments, such as ...
For example, a magnitude 7.0 quake in Salta, Argentina, in 2011, that was 576.8 km deep, had a maximum felt intensity of V, [19] while a magnitude 2.2 event in Barrow in Furness, England, in 1865, about 1 km deep, had a maximum felt intensity of VIII. [20] The small table is a rough guide to the degrees of the MMI scale.
Thus, a magnitude zero microearthquake has a seismic moment of approximately 1.1 × 10 9 N⋅m, while the Great Chilean earthquake of 1960, with an estimated moment magnitude of 9.4–9.6, had a seismic moment between 1.4 × 10 23 N⋅m and 2.8 × 10 23 N⋅m. Seismic moment magnitude (M wg or Das Magnitude Scale ) and moment magnitude (M w) scales
In Japan, for shallow (depth < 60 km) earthquakes within 600 km, the Japanese Meteorological Agency calculates [2] a magnitude labeled MJMA, M JMA, or M J. (These should not be confused with moment magnitudes JMA calculates, which are labeled M w (JMA) or M (JMA), nor with the Shindo intensity scale.)
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.