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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 original "body-wave magnitude" – mB or m B (uppercase "B") – was developed by Gutenberg 1945c and Gutenberg & Richter 1956 [25] to overcome the distance and magnitude limitations of the M L scale inherent in the use of surface waves. mB is based on the P and S waves, measured over a longer period, and does not saturate until around M 8.
The formula to calculate surface wave magnitude is: [3] = + (), where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s (usually 20 ± 2 seconds), Δ is the epicentral distance in °, and
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
On April 5, 2024, a magnitude 4.8 earthquake centered near Whitehouse Station, New Jersey struck the region; no injuries or damage were immediately reported. [20] This is the highest-magnitude earthquake in the region since 1884. An aftershock of magnitude 3.8 occurred that day close to Gladstone, New Jersey and was felt in Manhattan and ...
Distribution of seismic intensity observation points for the offshore Miyagi earthquakes in 1978 and 2005. The former had a magnitude of 7.4 with a maximum seismic intensity of 5, while the latter had a magnitude of 7.2 with a maximum seismic intensity of 6-. The density of observation points was higher in 2005.
[3]: 24 An earthquake with a magnitude of 5.5–6.0 is expected to occur every 50–100 years in the Texas Panhandle, while an earthquake with a magnitude greater than 6.0 is expected to occur every 300 years. [5] The strongest earthquake in this region was a magnitude 4.9 earthquake that occurred in 1925.
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.