![]() Prior to that, no agency was specifically focused on researching earthquake activity. California earthquakes (1769–2000)Īccording to seismologist Charles Richter, the 1906 San Francisco earthquake moved the United States Government into acknowledging the problem. Following destructive earthquakes in the late 19th and early 20th centuries, real estate developers, press, and boosters minimized and downplayed the risk of earthquakes out of fear that the ongoing economic boom would be negatively affected. By this time, scientists were well aware of the threat, but seismology was still in its infancy. While the 1812 San Juan Capistrano, 1857 Fort Tejon, and 1872 Owens Valley shocks were in mostly unpopulated areas and only moderately destructive, the 1868 Hayward event affected the thriving financial hub of the San Francisco Bay Area, with damage from Santa Rosa in the north to Santa Cruz in the south. ![]() Since the three damaging earthquakes that occurred in the American Midwest and the 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. From 1850–2004, there was about one potentially damaging event per year on average, though many of these did not cause serious consequences or loss of life. After the missions were secularized in 1834, records were sparse until the California Gold Rush in the 1840s. As Spanish missions were constructed beginning in the late 18th century, earthquakes records were kept. Ship captains and other explorers also documented earthquakes. state of California was documented in 1769 by the Spanish explorers and Catholic missionaries of the Portolá expedition as they traveled northward from San Diego along the Santa Ana River near the present site of Los Angeles. Learn more about the USGS Earthquake Hazards Program and ShakeAlert.The earliest known earthquake in the U.S. Visit the and Twitter accounts for the latest updates. The USGS operates a 24/7 National Earthquake Information Center in Colorado that can be reached for more information at 30. If you felt this earthquake, report your experience on the “USGS Did You Feel It?” website for this event. The Wireless Emergency Alert system did not distribute alerts for the earthquake because the underestimation of the quake meant it did not reach the system's threshold of alerting for earthquakes that are M5.0 or stronger. App providers, including MyShake, and QuakeAlertUSA, as well as Google Android have an alerting threshold of M4.5. The apps also sent alerts for a M4.6 aftershock at 23:33 UTC (4:33 pm local time) that was correctly located. ShakeAlert Messages were distributed via app partners for the inaccurately located M4.8 (near Stockton) that occurred as shaking from the M6.0 travelled across the state. As the USGS builds more stations, it expects to see most of these issues resolved. The system is constantly growing and learning from events like these. This can cause issues like inaccurately locating and miscalculating the quake. The system initially thought it was detecting three different smaller earthquakes rather than one larger one. With relatively few seismic stations in this part of California, earthquake waves have to travel further to be detected. The ShakeAlert Earthquake Early Warning System detected the earthquake 25.6 seconds after it started, but under-estimated the magnitude as a M4.8 at an estimated location that was about 31 miles (50 km) south of the actual location. ![]() For estimates of casualties and damage, visit the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) website. Visit the USGS earthquake event page for more information. The USGS is coordinating its response with the California Geological Survey and the University of Nevada at Reno. USGS scientists expect that this event will trigger aftershocks, but these will decrease in frequency over time. The event was widely felt, with over 25,000 "Did You Feel It?" reports thus far submitted. The quake is a result of normal faulting at approximately 6.2 miles (10 km) depth near the Antelope Valley fault, which runs north-south along the Sierra Nevada range front. Perceived shaking for the quake was very strong. The earthquake occurred about 20 miles southwest of Smith Valley, NV. ![]()
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