the 1971 san fernando earthquake An hour before sunrise, at 6:01 AM, PST, on February 9, 1971, the San Fernando region was struck by one of the most devastating earthquakes in California history. The red line is the fault on which the Northridge quake occurred in 1994. Never before had such a strong acceleration been recorded in an earthquake. On Feb. 9, 1971, the deadly San Fernando Earthquake rattled Southern California, leaving more than 60 people dead and causing more than $500 million in property damage. – and caused $553 million damage [in 1971 dollars, that would be about $3.28 billion in 2016 dollars]. The 1971 San Fernando-Sylmar earthquake, which measured 6.7 on the Richter scale of ground motion, occurred on a buried fault that was later named the Sierra Madre fault. Within the southern California region alone, the historic record suggests that an earthquake of about this magnitude occurs on the average of once every four years ( Fig. The unanticipated thrust earthquake had a moment magnitude of 6.5 or 6.7 (as determined by several independent institutions) and had a maximum Mercalli intensity of XI (Extreme). It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized. That’s because a fault with the provocative name of the Santa Susana thrust exhibited a lot of movement that day, with the result being an earthquake … Around 80,000 residents were required to evacuate from the area for three days due to fears that the whole area would be flooded by the dam’s water reserve. Earthquake Information Chronological Earthquake Index San Fernando Earthquake. The unreinforced concrete wings of the V.A Hospital, built in 1925, toppled leaving 47 dead and numerous victims trapped below the wreckage. The 1971 San Fernando earthquake (also known as the Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in … Mandatory Credit: Brue Cox/ The L.A. Times/ ME.Quake71.1.1Ð22Ðm2.7.$. | In some areas of the epicentral region the ground had shaken so violently that seismic sensors recorded accelerations of more than 1.25 g, where g is the standard gravitational acceleration at the Earth's surface. Dam failure As the dam might collapse further and then be breached by the enormous pressure of the water behind it, authorities decided to evacuate an area of 10 square miles along the San Diego Freeway. | My dad rushed us out and filmed some of the freeway damage. | | | More chunks of earth collapsed with each new aftershock, reducing the height of the crown and bringing the water table dangerously close to the top of the dam (see Figure 1). Mandatory Credit: Al Markado/ The Los Angeles Times, Los Angeles Times Contributor: Larry Sharkey (retired), The Ground Beneath our Feet: A Hundred Years of Earthquakes in Los Angeles. Teleseismic P, SV, and SH waves recorded by the WWSS and Canadian networks from the 1971 San Fernando, California earthquake (M L = 6.6) are modeled in the time domain to determine detailed features of the source as a prelude to studying the near and local field strong-motion observations. However, when you live in earthquake country, you might want to give the question a second thought. The question of whether it is wise to live below a dam behind which millions of acre feet of water are stored is usually rather low on people's lists of daily worries. Forty-six years ago today, the possibility of such a sudden dam burst was the hair-raising fear, in the chaos and devastation following the magnitude 6.7 earthquake that struck the San Fernando Valley north of Los Angeles. Damage from the 1971 quake. The earthquake was the third major earthquake to occur in the state in 23 years (after the 1971 San Fernando Valley and 1989 San Francisco–Oakland earthquakes), the Northridge earthquake was the state's most destructive one since the San Francisco earthquake of 1906 and the one that cost the most expensive for reconstruction. It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized." During the Northridge earthquake in January 1994, more than 50 people were killed and the quake caused damage worth $35 billion. It also occurred on a hitherto unknown fault, albeit a different one from the San Fernando fault (see Figure 2). The 1971 San Fernando earthquake, also known as Sylmar earthquake, struck the San Fernando Valley near Sylmar at 6:00:55 a.m. PST on February 9, 1971, with a magnitude of 6.6. Later, scientists at UCLA estimated that flooding following the collapse of the dam could have killed between 70,000 and 120,000 people. The 1971 San Fernando earthquake, also known as the “Sylmar Quake,” took place on the morning of February 9, 1971 around 6:01am. But even now, after further detailed studies, they are not sure whether they have identified all blind faults in the area or if the valley's inhabitants are in for more surprises. Even more surprising was the location of the focus of the quake, which later came to be known as the San Fernando earthquake. Earthquake hits the San Fernando Valley area of California. The 1971 earthquake was a massive disaster resulting in collapsed freeways, destroyed homes, and way too many ruined… But the threat of disaster didn't end when the shaking stopped. TYPE OF FAULTING: thrust TIME: February 9, 1971 / 6:01 am PST LOCATION: 34° 24.67' N, 118° 24.04' W MAGNITUDE: M W 6.5 DEPTH: 8.4 km FAULT INVOLVED: San Fernando fault zone; minor offset reported on the eastern Santa Susana fault zone The two blue lines mark the faults which ruptured in the San Fernando earthquake 46 years ago today. The 1971 San Fernando earthquake (also known as the Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. Following the San Fernando Earthquake, new seismic safety building codes and legislation such as the Alquist-Priolo Act, which bans development near active fault lines in California, were put into place. 1971 San Fernando earthquake map via USGS The M6.5 earthquake, also known as the Sylmar earthquake, killed 65 people and injured 2,000. The 6.6 magnitude earthquake with an epicenter located along a 12 mile fault zone below the San Gabriel Mountains lasted approximately 12 seconds and affected the entire San Fernando Valley. Most dams are constructed well and they are built for eternity. The presence in California of major universities with strong and active earthquake research In the end, the dam held and the evacuees were allowed to return to their homes. A little known fact was that the Van Norman … | Although the Richter magnitude of the tremblor was 6.6, … The 1971 San Fernando earthquake (also known as the 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 moment magnitude of 6.5 or 6.7 (as determined by several independent institutions) and had a maximum Mercalli intensity of XI (Extreme). A seismograph of the San Fernando earthquake in southern California in 1971 shows (top) ground acceleration, (center) velocity, and (bottom) displacement. The San Fernando earthquake of February 9, 1971, was a geologic phenomenon not unlike many similar earthquakes that occur every year around the world. Burbank, California - Wikipedia In the 1971 San Fernando earthquake, which took place along the western edge of the Sierra Madre Fault, surface ruptures were nearly 12 mi long, including one portion a few miles northwest of Glendale. Following these to earthquakes, geologists are now sure that many more of these hidden faults crisscross deep beneath the San Fernando Valley. (The earthquake of 9-Feb-1971). 1984 More than once have dams failed or were overtopped due to the shaking of large earthquakes - with devastating consequences for the people living downstream. 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