[10], Several key attributes of the event were shared with the 1994 Northridge earthquake, considering both were brought about by thrust faults in the mountains north of Los Angeles, and each resulting earthquake being similar in magnitude, though no surface rupture occurred in 1994. The shaking surpassed building code requirements and exceeded what engineers had prepared for, and although most dwellings in the valley had been built in the prior two decades, even modern earthquake-resistant structures sustained serious damage. The event affected a number of health-care facilities in Sylmar, San Fernando, and other densely populated areas north of central Los Angeles. The initial surveyors of the extensive faulting in the valley, foothills, and mountains reported only tectonic faulting, while excluding fissures and other features that arose from the effects of compaction and landsliding. 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. 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. As of 1973, a few of the highest risk (26 were completed in zone 3 alone) sites that had been completed were in Seattle, Memphis, Charleston, and Boston. Seismologists call it the San Fernando earthquake.USGS 'Sylmar Quake' or 'Sylmar earthquake' is the name initially given to the event by local media outlets, because the worst damage … The maximum slip was up to 2 meters (6 feet). Few of the slides that were logged from the air were also observed from the ground. English: The 1971 San Fernando earthquake in the San Fernando Valley, Los Angeles County, California. [16], 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. Even at that time, engineers were against the idea of constructing buildings to resist the high forces that were seen in the El Centro shock, but after a 1966 earthquake peaked at .5g, and a maximum of 1.25g was observed at the Pacoima Dam during the San Fernando event, debate began as to whether that low requirement was sufficient. The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. 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. 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. In 1969, the California Division of Mines and Geology published Map Sheet 15, entitled Preliminary reconnaissance map of major landslides, San Gabriel Mountains, California, by D. M. Morton and R. Streitz. Ground displacement damaged sidewalks and roads, with cracks in the more rigid asphalt and concrete often exceeding the width of the shift in the underlying soil. The southern California soil shook violently the morning of February 9, 1971. [26][27], Introduced as Senate Bill 520 and signed into law in December 1972, this legislation was originally known as the Alquist-Priolo Geologic Hazard Zones Act, and had the goal of reducing damage and losses due to surface fault ruptures or fault creep. Messrs. Gray and Caldwell went immediately to the Los Angeles District Office where they maintained constant contact with field, administrative, and disaster staffs. The unanticipated thrust earthquake had a magnitude of 6.5 on the Ms scale, and a maximum Mercalli intensity of XI (Extreme). By that time, much of the area had been built over; new base maps were available, and many new roads provided road cuts to give new looks at the geology. [24], This interchange is a broad complex of overpasses and bridges that was nearly complete at the time of the earthquake and not all portions were open to traffic. A band of similarly intense damage further away near Ventura Boulevard at the southern end of the valley was also identified as having been related to soil type. Nursing homes also were affected. A state of emergency in California after the most serious earthquake since the San … [17], The damage was greatest near and well north of the surface faulting, and at the foot of the mountains. The movement contributed to heavy damage at the Sylmar Juvenile Hall facility, Sylmar Converter Station, and the Metropolitan Water District Treatment Plant, but its effects on the interchange was not completely understood as of a 1971 report from the California Institute of Technology. The westbound I-210 to southbound I-5, which was complete except for paving at the ramp section, collapsed to the north, likely because of vibration that moved the overpass off its supports due to an inadequate seat. Had the earthquake hit at rush hours, when the streets and freeways were full of traffic; had it hit during school hours, when schools were filled with children--our grief might be much greater. No need to register, buy now! Charlie Bishop came from San Francisco, as well as several staff members from Sacramento-Quint Aune, Chief Wes Bruer, Bob Matthews, and Bennie Troxel. Considerable damage was seen in localized portions of the valley and also in the foothills of the San Gabriel Mountains above the fault block. All these buildings had been previously inspected with regard to the requirements of the Act, and many were reinforced or rebuilt at that time, but earthquake engineering experts recommended further immediate refurbishment or demolition after a separate evaluation was done after the February 1971 earthquake, and within a year and a half the district followed through with the direction with regard to about 100 structures. "[14], The USGS commissioned a private company and the United States Air Force to take aerial photographs over 97 sq mi (250 km2) of the mountainous areas north of the San Fernando Valley. [16], 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. They were supported by aircraft: a fixed wing chartered plane and a helicopter provided and manned by the U. S. Marine Corps. The two facilities, located near Grapevine and Weldon canyons that channel water and debris off the Sierra Madre Mountains, are lined by steep ridges and have formed alluvial fans at their mouths. Also known as the Sylmar Earthquake, this earthquake occurred on the San Fernando fault zone, a zone of thrust faulting which broke the surface in the Sylmar-San Fernando Area. Peter Fischer, of Whittier College, had the foresight and was instrumental in making arrangements for Marine Corps support. The earthen lip of the dam fell into the reservoir and brought with it the concrete lining, while what remained of the dam was just 5 feet (1.5 m) above the water level. 1971 San Fernando Earthquake Collapsed Freeway Overpasses Photo. The gray zones represent areas with unsafe wood-frame dwellings (the locations of which are shown by a diamond symbols). Several landslides occurred between Balboa Boulevard and California State Route 14, but the most significant damage occurred at the two major interchanges. The 1971 San Fernando (a.k.a. 8 x 10 in. 1971 San Fernando (California) Earthquake Archive. Damage from the 1971 quake. The 1971 earthquake has enabled him to add another facet to the study of the area he now knows so well. At 2 mi (3.2 km), Hubbard Street Elementary School was the closest school to Pacoima dam, and was also less than a mile from the Veterans Hospital complex. The Field Act was put into effect just one month following the destructive March 1933 Long Beach earthquake that damaged many public school buildings in Long Beach, Compton, and Whittier. [19], On the grounds, there were cracks in the pavement and soil, but no surface faulting. The Los Angeles Unified School District had 660 schools consisting of 9,200 buildings at the time of the earthquake, with 110 masonry buildings that had not been reinforced to meet the new standards. 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. This was done as a precaution to accommodate further collapse due to a strong aftershock. 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. 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. Analysis revealed that the earthquake triggered over 1,000 landslides. Shear cracking occurred at the column closest to the western abutment, and the ground at the same column's base exhibited evidence of rotation. The upstream slope of Lower San Fernando Dam failed during the 1971 San Fernando earthquake (Seed et al. 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. Full Record They paid particular attention to hillsides that might give way in aftershocks, causing more havoc than already existed. Earthquake Damage Photos . Except for the concrete gymnasium, all of the buildings at Sylmar High School (3.75 mi (6.04 km) from Pacoima Dam) were post-Field Act, one-story, wood construction. The area where the heaviest effects were present was limited by geographical features on the three remaining margins, with the Santa Susana Mountains on the west, the Santa Monica Mountains and the Los Angeles River to the south, and along the Verdugo Mountains to the east. The Los Angeles Department of Water and Power, as well as the County of Los Angeles, investigated and verified that local soil conditions contributed to the ground displacement and resulting destruction. [26], Despite the compelling seismogram from the 1940 event in El Centro, strong-motion seismology was not explicitly sought until later events occurred—the San Fernando earthquake made evident the need for more data for earthquake engineering applications. Intact blocks of embankment material moved tens of feet on liquefied hydraulic fill shell material (figures D-8-1 and D-8-2). [21], Differential ground motion and strong shaking (MMI VIII (Severe)) were responsible for serious damage to the Sylmar Juvenile Hall facility and the Sylmar Converter Station (both located close to the Upper Van Norman lake). [23], While the Newhall Pass interchange was still under construction at the time of the earthquake, the requisite components of the overpass were complete. The Indian Hills Medical Center, the Foothill Medical Building, and the Pacoima Lutheran Professional building were heavily damaged. Since it is presumed that surface rupture will likely take place where past surface displacement has occurred, the state geologist was given the responsibility for evaluating and mapping faults that had evidence of Holocene rupture, and creating regulatory zones around them called Earthquake Fault Zones. Damage from the San Fernando Earthquake of 1971 was mostly to freeway overpasses and hospitals. [22], Substantial disruption to about 10 miles of freeways in the northern San Fernando Valley took place, with most of the damage occurring at the Foothill Freeway / Golden State Freeway interchange, and along a five-mile stretch of Interstate 210. Damage was locally severe in the northern San Fernando Valley and surface faulting was extensive to the south of the epicenter in the mountains, as well as urban settings along city streets and neighborhoods. 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. Accentuated damage near alluvium had been documented during the investigation of the effects of the 1969 Santa Rosa earthquakes. The act restricts construction of buildings designed for human occupancy across potentially active faults. 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. [11], 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. [19], The Veterans Administration Hospital entered into service as a tuberculosis hospital in 1926 and became a general hospital in the 1960s. The narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion. Northridge, CA Earthquake 1994 - Miscellaneous Pictures - … Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. This made the earthquake the most documented event, at the time, in terms of strong-motion seismology; by comparison, the 1964 Alaska earthquake did not provide any strong motion records. [18], Federal, county, and private hospitals suffered varying degrees of damage, with four major facilities in the San Fernando Valley suffering structural damage, and two of those collapsing. There was evidence to suggest the slope failure took place after the shaking had stopped. Moving eastward, there is the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, with active reverse faults (San Cayetano, Red Mountain, Santa Susana, and Sierra Madre) all lining the north boundary. Olive View Hospital, a county-owned structure, is such a lesson. Severe structural damage caused by the San Fernando earthquake corresponds to an intensity of IX, and locally X, and so it appears that the 1893 shock was the lesser of the two. It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized." The building was not in use and remained standing. On the day following the earthquake, State Geologist Wesley Bruer convened a meeting of more than 40 geologists and seismologists engaged in studying the earthquake, so that all investigative activities might be coordinated. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. This paper compares the distribution of damage from the San Fernando, 1971, and Northridge, 1994, earthquakes. The San Fernando earthquake has been extensively studied by many seismologists, geologists, and earthquake engineers. One hundred seventy-five of the recordings came from these buildings, another 30 were on hydraulic structures, and the remainder were from ground-based installations near faults, including an array of the units across the San Andreas Fault. On Interstate 5, the most significant damage was between the Newhall Pass interchange on the north end and the I-5 / I-405 interchange in the south, where subsidence at the bridge approaches and cracking and buckling of the roadway made it unusable. There are various names for this earthquake. 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