What was the name of the earthquake in February 1971?
/ 34.27; -118.41 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.
How many people died in the 1971 San Fernando 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. Also known as the Sylmar Earthquake, the magnitude-6.5 quake was reported on a Tuesday at about 6:01 a.m.
What time does the San Fernando earthquake occur?
The San Fernando earthquake occurred on February 9 at 6:00:41 am Pacific Standard Time (14:00:41 UTC) with a strong ground motion duration of about 12 seconds.
When was the last time an earthquake happened on the same day?
The quake hit on the same day as major quakes in 1985 and 2017. Alarms for Monday's quake came less than an hour after alarms sounded in a nationwide earthquake simulation to mark the previous quakes.
How long did the 1971 earthquake last?
about 60 secondsThe San Fernando earthquake occurred on February 9, 1971, at 6:00:41 am Pacific Standard Time (14:00:41 UTC) with a strong ground motion duration of about 12 seconds as recorded by seismometers, although the whole event was reported to have lasted about 60 seconds.
When was the 1971 earthquake in LA?
Feb. 9, 1971Also known as the San Fernando earthquake, the Feb. 9, 1971, magnitude-6.5 quake struck at about 6:01 a.m. Its origin was in the foothills of the San Gabriel Mountains north of Los Angeles, but shaking was felt across a widespread part of the San Fernando Valley.
What caused the 1971 San Fernando earthquake?
The San Fernando Fault is a thrust fault, which means a section of land above the fault moved up and over a region below it. The earthquake was a single episode of ongoing crustal deformation, which, in a local sense, has pushed the San Gabriel Mountains up and south towards the broader Los Angeles Basin.
How many people died in the 1971 Sylmar earthquake?
64 deathsThe magnitude 6.6 Sylmar earthquake that shook Southern California on Feb. 9, 1971, caused significant damage and 64 deaths.
How big was the 1971 earthquake in LA?
On February 9, 1971 at 6:01 am PST, a devastating M6. 6 earthquake struck the densely populated metropolitan area of Los Angeles, leaving death and destruction in its wake. The epicenter of the earthquake was in the vicinity of Magic Mountain, about six miles northeast of Sylmar, at a depth of about seven miles.
When was the worst earthquake in LA?
On the early morning of June 28, 1992, a magnitude 7.3 (Mw) earthquake—the largest Southern California earthquake in 40 years—struck, rupturing five different faults! Although its epicenter was in a sparsely populated area, it was said to have been felt throughout the Los Angeles area, Arizona, Nevada, and Idaho.
Is a 10.0 earthquake possible?
No, earthquakes of magnitude 10 or larger cannot happen. The magnitude of an earthquake is related to the length of the fault on which it occurs. That is, the longer the fault, the larger the earthquake.
What was the strongest earthquake in California?
It was “the largest earthquake to strike the contiguous United States in 40 years,” according to the United States Geological Survey. In 1989, a 6.9 earthquake hit Loma Prieta, Calif. It felled Bay Area freeway interchanges, interrupted a World Series and caused $10 billion in damage.
What was the worst earthquake in California history?
California's Largest Recorded Earthquakes Since 1800, Ranked by MagnitudeMagnitudeDateLocation7.9Jan. 9, 1857Fort Tejon7.8April 18, 1906San Francisco7.4Mar. 26, 1872Owens Valley7.4Nov. 8, 1980W. of Eureka*12 more rows
How long did Northridge earthquake last?
10–20 secondsIts epicentre was in Reseda, a suburb located about 23 miles (37 km) west-northwest of downtown Los Angeles. The major shock lasted 10–20 seconds and registered a magnitude of 6.7.
What is the average time for great earthquakes to occur?
about once a yearOn average, Magnitude 2 and smaller earthquakes occur several hundred times a day world wide. Major earthquakes, greater than magnitude 7, happen more than once per month. "Great earthquakes", magnitude 8 and higher, occur about once a year.
Was there an earthquake in 1972?
On Friday, September 15 » 1972, shortly after midnight, an earthquake shook a seven-state area of the central United States.
What was the magnitude of the 1971 Sylmar earthquake?
— At 6 a.m. on February 9, 1971, a 6.6-magnitude earthquake struck the San Fernando Valley.
What was the biggest earthquake in California?
In 1992, a 7.3 earthquake struck near Landers. It was “the largest earthquake to strike the contiguous United States in 40 years,” according to the United States Geological Survey. In 1989, a 6.9 earthquake hit Loma Prieta, Calif.
When was the last strong earthquake in California?
July 5, 2019California's Largest Recorded Earthquakes Since 1800, Ranked by MagnitudeMagnitudeDateLocation7.1July 5, 2019Ridgecrest/Trona7.0May 18, 1940El Centro6.9Oct. 17, 1989Bay Area6.7Jan. 17, 1994Northridge12 more rows
How long was the Northridge earthquake?
approximately 10–20 secondsThe quake had a duration of approximately 10–20 seconds, and its peak ground acceleration of 1.82 g was the highest ever instrumentally recorded in an urban area in North America. Shaking was felt as far away as San Diego, Turlock, Las Vegas, Richfield, Phoenix and Ensenada.
What year did the San Fernando earthquake happen?
The 1971 San Fernando Earthquake damaged a pipe on the Maclay Reservoir outlet line in Sylmar.
Where was the San Fernando earthquake?
This map illustrates widespread shaking from the 1971 San Fernando earthquake in Southern California.
How many people died in the San Fernando 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. Also known as the Sylmar Earthquake, the magnitude-6.5 quake was reported on a Tuesday at about 6:01 a.m.
What was the name of the dam that collapsed after the San Fernando earthquake?
This aerial view shows a collapsed section of the lower Van Norman Dam after the 1971 San Fernando Earthquake. An aerial view of displaced railroad tracks in Sylmar after the 1971 San Fernando Earthquake. A view inside Olive View Medical Center after the 1971 San Fernando Earthquake.
What happened to the 405 freeway?
Residents along the 405 Freeway were evacuated for days until the dam was shored up and determined to be safe. The aftermath led to major changes for building construction and the Alquist-Priolo Act. It bans construction on active faults in California. Below, a look back at the 1971 Sylmar Earthquake.
When was the Sylmar earthquake?
Below, a look back at the 1971 Sylmar Earthquake.
What hospital was damaged in the Sylmar earthquake?
Both the Veteran's Administration Hospital and Olive View Medical Center in Sylmar were severely damaged, accounting for many of the deaths. Much like the Northridge Earthquake 23 years later, the quake also tore apart freeway overpasses. But the threat of disaster didn't end when the shaking stopped.
When was the San Fernando earthquake?
See also: California earthquake forecast and Earthquake rupture. The San Fernando earthquake occurred on February 9, 1971, at 6:00:41 am Pacific Standard Time (14:00:41 UTC) with a strong ground motion duration of about 12 seconds as recorded by seismometers, although the whole event was reported to have lasted about 60 seconds.
How many people died in the San Fernando earthquake?
Casualties. 58–65 dead. 200–2,000 injured. 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.
How high was the acceleration of the Pacoima Dam?
The instrument that was installed at the Pacoima Dam recorded a peak horizontal acceleration of 1.25 g , a value that was twice as large as anything ever seen from an earthquake. The extraordinarily high acceleration was just one part of the picture, considering that duration and frequency of shaking also play a role in how much damage can occur. The accelerometer was mounted on a concrete platform on a granite ridge just above one of the arch dam 's abutments. Cracks formed in the rocks and a rock slide came within 15 feet (4.6 m) of the apparatus, and the foundation remained undamaged, but a small (half-degree) tilt of the unit was discovered that was apparently responsible for closing the horizontal pendulum contacts. As a result of what was considered a fortunate accident, the machine kept recording for six minutes (until it ran out of paper) and provided scientists with additional data on 30 of the initial aftershocks.
How did the Newhall Pass overpass collapse?
The spans slipped off of their supports at either end due to lack of proper ties and insufficient space (a 14 in (360 mm) seat was provided) on the support columns. Ground displacement at the site was ruled out as a major cause of the failure, and in addition to the fallen sections and a crane that was struck during the collapse, other portions of the overpass were also damaged. Shear cracking occurred at the column closest to the western abutment, and the ground at the same column's base exhibited evidence of rotation.
Where is the San Fernando fault zone?
Prominent surface faulting trending N72°W was observed along the San Fernando Fault Zone from a point south of Sylmar, stretching nearly continuously for 6 miles (9.7 km) east to the Little Tujunga Canyon. Additional breaks occurred farther to the east that were in a more scattered fashion, while the western portion of the most affected area had less pronounced scarps, especially the detached Mission Wells segment. Although the complete Sierra Madre Fault Zone had previously been mapped and classified by name into its constituent faults, the clusters of fault breaks provided a natural way to identify and refer to each section. As categorized during the intensive studies immediately following the earthquake, they were labeled the Mission Wells segment, Sylmar segment, Tujunga segment, Foothills area, and the Veterans fault.
How many landslides were there in the San Fernando Valley?
Analysis revealed that the earthquake triggered over 1,000 landslides. Highly shattered rock was also documented along the ridge tops, and rockfalls (which continued for several days) were the result of both the initial shock and the aftershocks. Few of the slides that were logged from the air were also observed from the ground. The greatest number of slides were centered to the southwest of the mainshock epicenter and close to the areas where surface faulting took place. The slides ranged from 49–984 feet (15–300 m) in length, and could be further categorized as rock falls, soil falls, debris slides, avalanches, and slumps. The most frequently encountered type of slide was the surficial (less than 3 feet (0.91 m) thick) debris slides and were most often encountered on terrain consisting of sedimentary rock.
What happened to the Olive View Medical Center?
The Olive View Medical Center and Veterans Hospital both experienced very heavy damage, and buildings collapsed at both sites, causing the majority of deaths that occurred. The buildings at both facilities were constructed with mixed styles, but engineers were unable to thoroughly study the buildings' responses because they were not outfitted with instruments for recording strong ground motion, and this prompted the Veterans Administration to later install seismometers at its high-risk sites. Other sites throughout the Los Angeles area had been instrumented as a result of local ordinances, and an unprecedented amount of strong motion data was recorded, more so than any other event up until that time. The success in this area spurred the initiation of California's Strong Motion Instrumentation Program.
The USGS has up-to-date details on the July 5, 2019 event
Updated on July 19. Visit the USGS earthquake event page for more information.
Updated on July 12. Visit the USGS earthquake event page for more information
Scientists from the USGS and other organizations continue field work and analyses to learn more about the series of earthquakes and aftershocks centered in the Southern California desert near Ridgecrest.
Updated on July 9, 2019
According to the current forecast, during the week beginning on July 8, 2019, there is less than a 1 % chance of one or more aftershocks that are larger than magnitude 7.1, and an 8 % chance of a magnitude 6 or larger aftershock. Smaller earthquakes are likely during the next week, with 55 to 120 magnitude 3 or greater aftershocks.
Updated on July 8, 2019
The July 5, 2019 magnitude 7.1 earthquake near eastern California’s Searles Valley resulted from shallow strike-slip faulting in the North America plate crust. The magnitude 7.1 event occurred about 34 hours after and about 7 miles northwest of a magnitude 6.4 foreshock on July 4, 2019 at 10:34 a.m. Pacific Time.
Updated on July 6, 2019
USGS scientists and crews continue to work around the clock on field work, mapping impacted areas and monitoring additional aftershocks to keep the public informed.
Posted July 6, 2019
A magnitude 7.1 earthquake struck southern California on July 5, 2019 at 8:20 p.m. local time (July 6 at 03:20 UTC). This event was centered near the July 4, 2019 magnitude 6.4 earthquake.
Where was the San Gabriel earthquake?
The earthquake was centered in the San Gabriel Mountains about nine miles north of San Fernando. The surface of the earth ruptured for about 10 miles, from Sunland through Sylmar.
How many earthquakes were there in the area where the fault broke?
In fact, the area where the fault broke had been the locale of only 10 earthquakes of magnitude 3.0 or greater in the previous 37 years.
How many people died in the San Fernando earthquake?
The results were not as fortunate at the San Fernando Veterans Administration Hospital, where 47 of the 64 fatalities attributed to the San Fernando quake occurred.
What magnitude was the San Fernando earthquake?
Scientists now believe what they call simply the San Fernando earthquake was a magnitude 6.7, identical in strength to the Northridge quake.
How much water was in the dam in 1971?
The 1,100-foot dam held 3.6 billion gallons of water on the morning of Feb. 9, 1971, but it was only half full; the water level was 36 feet below the lip.
Who said the toll might not have been that high, but a dam failure would have been a disaster unique?
Clarence Allen , Caltech professor emeritus of seismology , said the toll might not have been that high, but a dam failure would have been “a disaster unique in American history.”
Was the San Fernando earthquake a catastrophe?
The San Fernando quake, in fact, could have been a catastrophe instead of just a costly disaster. That conclusion arises from its most striking episode: the near-collapse of the lower dam at the Van Norman reservoir.
Overview
Earthquake
The San Fernando earthquake occurred on February 9, 1971, at 6:00:41 am Pacific Standard Time (14:00:41 UTC) with a strong ground motion duration of about 12 seconds as recorded by seismometers, although the whole event was reported to have lasted about 60 seconds. The origin of faulting was located five miles north of the San Fernando Valley. Considerable damage was seen i…
Tectonic setting
The San Gabriel Mountains are a 37.3 mi (60.0 km) long portion of the Transverse Ranges and are bordered on the north by the San Andreas Fault, on the south by the Cucamonga Fault, and on the southwest side by the Sierra Madre Fault. The San Bernardino, Santa Ynez, and Santa Monica Mountains are also part of the anomalous east–west trending Transverse Ranges. The domain of the ranges stretches from the Channel Islands offshore to the Little San Bernardino Mountains, 3…
Damage
The areas that were affected by the strongest shaking were the outlying communities north of Los Angeles that are bounded by the northern edge of the San Fernando Valley at the base of the San Gabriel Mountains. The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. The area where the heaviest effec…
Aftermath
Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. After the M6.4 1933 Long Beach earthquake, the Field Act was passed the following month, and after the 1989 Loma Prieta earthquake, the Seismic Hazards Mapping Act and Senate Bill 1953 (hospital safety requirements) were established. Following the San Fern…
See also
• 1994 Northridge earthquake, a magnitude 6.7 quake which affected many of the same areas
• California State Route 126
• Interstate 105 (California)
• List of earthquakes in 1971
Further reading
• Bouchon, M. (1978). "A dynamic source model for the San Fernando earthquake". Bulletin of the Seismological Society of America. 68 (6): 1555–1576. doi:10.1785/BSSA0680061555. S2CID 132403783.
• Gaudreau, É.; Hollingsworth, J.; Nissen, E.; Funning, G. (2022), Complex 3-D surface deformation in the 1971 San Fernando, California earthquake reveals static and dynamic controls on off-fault deformation, Wiley, doi:10.1002/essoar.10511699.1
External links
• San Fernando Earthquake – Southern California Earthquake Center
• Historic Earthquakes – San Fernando, California – United States Geological Survey
• California Geological Survey – About CSMIP – California Department of Conservation