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Since the three damaging earthquakes that occurred in the American Midwest and the United States East Coast (1755 Cape Ann, 1811–12 New Madrid, 1886 Charleston) were well known, it became apparent to settlers that the earthquake hazard was different in California. While the 1812 San Juan Capistrano, 1857 Fort Tejon, and 1872 Owens Valley ...
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]
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic ...
Magnitude of the earthquake and aftershocks. The 1994 Northridge earthquake affected the Los Angeles area of California on January 17, 1994, at 04:30:55 PST. The epicenter of the moment magnitude 6.7 (Mw) blind thrust earthquake was beneath the San Fernando Valley. [3] Lasting approximately 8 seconds and achieving the largest peak ground ...
The 1989 Loma Prieta earthquake occurred on California's Central Coast on October 17 at 5:04 p.m. local time. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz County, approximately 10 mi (16 km) northeast of Santa Cruz on a section of the San Andreas Fault System and was named for the nearby Loma Prieta Peak in the Santa Cruz Mountains.
The most notable of these earthquakes is the 1872 Owens Valley earthquake, with an estimated magnitude of 7.4 M w (preferred; other estimates range as high as 7.9 [114]). The Owens Valley quake is believed to be the greatest earthquake on record and not just for California, but also for the western continental United States. [115]
The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a magnitude of 6.5 on the Ms scale and 6.6 on the Mw scale, and a maximum Mercalli intensity of XI (Extreme).
2014 South Napa earthquake. The 2014 South Napa earthquake occurred in the North San Francisco Bay Area on August 24 at 03:20:44 Pacific Daylight Time. At 6.0 on the moment magnitude scale and with a maximum Mercalli intensity of VIII (Severe), the event was the largest in the San Francisco Bay Area since the 1989 Loma Prieta earthquake.