This early and continuing exchange has added significantly to the effectiveness of the investigations. Apr 18, 2012 - Olive View Medical Center after the 1971 Sylmar Earthquake Transportation around the Los Angeles area was severely afflicted with roadway failures and the partial collapse of several major freeway interchanges. Because the first floor almost collapsed, the building was leaning to the north by almost two feet, and three of the four concrete stair towers fell away from the main building. The narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion. The Indian Hills Medical Center, the Foothill Medical Building, and the Pacoima Lutheran Professional building were heavily damaged. Other sites throughout the Los Angeles area had been instrumented as a result of local ordinances, and an extraordinary amount of strong motion data was recorded, more so than any other event up until that time. The greatest number of slides were centered to the southwest of the mainshock epicenter and close to the areas where surface faulting took place. As had happened following other earthquakes in California, legislation related to building codes was once again revised, with laws that specifically addressed the construction of homes or businesses near known active fault zones. A preliminary report of their investigations is presented in this magazine. 1971 San Fernando Earthquake Collapsed Freeway Overpasses Photo. The California Strong Motion Instrumentation Program was initiated in 1971 with the goal of maximizing the volume of data by furnishing and maintaining instruments at selected lifeline structures, buildings, and ground response stations. Since the collapse of the dam lowered its overall height, the decision to reduce its capacity proved to be a valuable bit of insurance. Though the reinforced concrete block structure was afflicted by the shock and uplift, the relatively good performance was in stark contrast to that of the Olive View and Veterans Hospital complexes. The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. Although instruments had recorded a force of .33g during the 1940 El Centro earthquake, building codes only required structures to withstand a lateral force of .1g as late as the 1960s. As a result, building of new structures for human occupancy across active fault lines was banned. 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. This destructive earthquake occurred in a sparsely populated area of the San Gabriel Mountains, near San Fernando. Some canals in the area of the dams were damaged and not usable, and dikes experienced slumping but these did not present a hazard. There was evidence to suggest the slope failure took place after the shaking had stopped. , The San Gabriel Mountains with the Veterans Hospital complex in center (above) and selected cities with reported felt intensity in the United States (below), Ground level and overhead view of the scarp at the Foothill Nursing Home, Los Angeles Department of Water and Power, Interstate 210 and State Route 210 (California), List of Los Angeles Unified School District schools, "Preliminary strong-motion results from the San Fernando earthquake of February 9, 1971", "Tectonic setting of the San Gabriel mountains", "Seismically triggered landslides in the area above the San Fernando Valley", "The study of earthquake questions related to Veterans Administration hospital facilities", "Damage to constructed works, associated with soil movements and foundation failures", "Ground displacement at San Fernando Valley Juvenile Hall and the Sylmar Converter Station", "Highway damage in the San Fernando earthquake", "Earthquake damage to freeway structures", "History of the Alquist-Priolo Earthquake Fault Zoning Act, California, USA", "San Fernando 1971: M 6.6 - 10km SSW of Agua Dulce, CA", "Seismological studies of the San Fernando earthquake and their tectonic implications", "Strong motion data from the San Fernando, California, earthquake of February 9, 1971", "Pattern of faulting and nature of fault movement in the San Fernando earthquake", "Building damage in the San Fernando Valley", Historic Earthquakes – San Fernando, California, California Geological Survey – About CSMIP, Veterans Memorial Community Regional Park, Los Angeles County Department of Parks and Recreation, https://en.wikipedia.org/w/index.php?title=1971_San_Fernando_earthquake&oldid=1001027502, Geology of Los Angeles County, California, February 1971 events in the United States, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License, This page was last edited on 17 January 2021, at 22:28. , Most of the buildings at the Los Angeles County–owned, 880-bed hospital complex had been built before the adoption of new construction techniques that had been put in place after the 1933 Long Beach earthquake. In addition to the collapse of the stairways, the elevators were out of commission. , 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. The origin of faulting was located five miles north of the San Fernando Valley. Recordprocessed by the JetPropulsion Laboratory, Pasadena; made avail able by the Earthquake Engineering Research Laboratory, California In 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. 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. Although the county engineer has rated the medical care and treatment center and the psychiatric unit as total losses, for an estimated $31 million dollars, 615 patients and 300 staff members were safely evacuated. The greatest damage was in the San Fernando area, near the front of the San Gabriel Mountains, where three hospitals were badly damaged (one of them accounting for the greatest loss of lives). Casualties in these highly affected areas might have increased had the shock occurred later in the day. Thus the San Fernando earthquake occurred in an area which has had relatively low seismicity and was not caused by movement on a major, historically active fault, such as the San Andreas or one of its branches. The lower dam was very close to breaching, and approximately 80,000 people were evacuated for four days while the water level in the reservoir was lowered. Three Division geologists had an especial interest in the area, as well as especial expertise. Vibration caused two of the bridge's 191-foot sections to fall from a maximum height of 140 ft (43 m), along with one of the supporting pillars. As we go to press one month later, 65 lives have been charged to it, and damage has been estimated at more than half a billion dollars. Abundant cracks formed in the ground at the site, and some foundations and many sidewalks were also cracked. It lasted about 60 seconds, and, in that brief span of time, took 65 lives, injured more than 2,000, and caused property damage estimated at $505 million. The 1971 San Fernando Earthquake. 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. By the late 1980s, the program had instrumented more than 450 structures, bridges, dams, and power plants. 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 damage was greatest near and well north of the surface faulting, and at the foot of the mountains. 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 one-story Foothill Nursing Home sat very close to a section of the fault that broke the surface and was raised up three feet higher than the street. 100% satisfaction guaranteed. Upon revisiting the scene of his earlier mapping, Mr. Saul was able to recognize that movement had taken place on the Santa Susana thrust, in the Bee Canyon area. By 1971, the facility comprised 45 individual buildings, all lying within 5 km (3.1 mi) of the fault rupture in Sylmar, but the structural damage was found to have occurred as a result of the shaking and not from ground displacement or faulting. 1971 San Fernando (California) Earthquake Archive. No need to register, buy now! The near total failure of the Lower Van Norman Dam resulted in the evacuation of tens of thousands of downstream residents, though an earlier decision to maintain the water at a lower level may have contributed to saving the dam from being overtopped. 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. The damaged buildings variously were wood-frame and masonry structures. There are various names for this earthquake. , Few strong motion seismometer installations were present outside of the western United States prior to the San Fernando earthquake but, upon a recommendation by the Earthquake and Wind Forces Committee, the Veterans Administration entered into an agreement with the Seismological Field Service (then associated with NOAA) to install the instruments at all VA sites in Uniform Building Code zones two and three. The hospital buildings, the freeway overpasses, and the Sylmar Juvenile Hall were on coarse alluvium that overlay thousands of feet of loosely consolidated sedimentary material. Along the hill fronts of the Tujunga segment some ambiguous formations were present because some scarps may have had influence from downhill motion, but for the most part they were tectonic in nature. 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. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. , 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. Twenty-six buildings that were built prior to 1933 had been constructed following the local building codes and did not require seismic-resistant designs. State and local agencies (as well as the property owner) were then responsible for enforcing or complying with the building restrictions. Although the Richter magnitude of the tremblor was 6.6, ranking it as moderate to large, but not great, it shook a wide, heavily populated area, leaving death and destruction in its wake. 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. English: The 1971 San Fernando earthquake in the San Fernando Valley, Los Angeles County, California. 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. osti.gov technical report: damage survey, san fernando earthquake of february 9, 1971. The list of items needing improvements included building codes, dams and bridges being made more earthquake resistant, hospitals that are designed to remain operational, and the restriction of development near known fault zones. 1975). Black and white photograph. , Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. Find art you love and shop high-quality art prints, photographs, framed artworks and posters at Art.com. One of the hardest-hit buildings was the just-completed San Fernando Veterans Administration Hospital, whose unreinforced concrete wings collapsed, killing at … By the time the sun had risen, ten geologists from the Los Angeles District Office of the California Division of Mines and Geology were in the field to appraise the geologic effects and to search for further potential hazards created by the earthquake. It was an expensive and heartbreaking lesson, but California has learned something, and can take heart. 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. A small number of damaging events have occurred, with three in Santa Barbara (1812, 1925, and 1978) and two in the San Fernando Valley (1971 and 1994), though other faults in the basin that have high Quaternary slip rates have not produced any large earthquakes. , Both the Upper and Lower Van Norman dams were severely damaged as a result of the earthquake. On February 9th, 1971, at approximately 6:00am, the foothills of the San Gabriel Mountains were struck by a 6.7 earthquake. Few of the slides that were logged from the air were also observed from the ground. , Paleomagnetic evidence has shown that the western Transverse Ranges were formed as the Pacific Plate moved northward relative to the North American Plate. It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized." , While the Newhall Pass interchange was still under construction at the time of the earthquake, the requisite components of the overpass were complete. More than 400 portable classrooms and 53 wood frame pre-Field Act buildings were also in use. The building was not in use and remained standing. It had been established that these zones had a higher likelihood of experiencing strong ground acceleration, and the plan was made to furnish the selected VA hospitals with two instruments. 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. , 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. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information The largest cumulative amount of slip of 6 feet 7 inches (2.01 m) occurred along the Sylmar and Tujunga segments. Messrs. Gray and Caldwell went immediately to the Los Angeles District Office where they maintained constant contact with field, administrative, and disaster staffs. The success of the Imperial Valley event was especially pronounced because of a recently constructed and fully instrumented government building that was shaken to the point of failure. The unanticipated thrust earthquake had a magnitude of 6.5 on the M s scale, and a maximum Mercalli intensity of XI (Extreme).The event was one in a series that affected the Los Angeles area in the late … Nursing homes also were affected. February 9, 1971, Granada Hills, CA. The San Bernardino, Santa Ynez, and Santa Monica Mountains are also part of the anomalous east–west trending Transverse Ranges. Dr. Morton's paper herein describes an additional 1,000 landslides generated by the earthquake--most of them west of the area previously mapped, but many in Big Tujunga Canyon, the site of already mapped slides. When it was apparent that the landslide potential of the hillsides, though great, did not threaten any urban areas, the geologists turned their attention to the study of geologic effects--so often ephemeral--and to other geologic hazards that may have been developed or increased by the 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 much as 5 ft (1.5 m) of lateral motion was observed on either end of the slide, and trenches that were excavated during the examination at the site revealed that some of the cracks were up to 15 ft (4.6 m) deep. Several landslides occurred between Balboa Boulevard and California State Route 14, but the most significant damage occurred at the two major interchanges. The two geologists Carl Wentworth and Robert Yerkes from the US Geological Survey in Pasadena later wrote that "the San Fernando fault was discovered to be active only when it ruptured the ground surface on February 9, 1971. Freeway interchanges collapsed (killing two men in a pickup truck under one fallen overpass), reservoirs were in danger of imminent failure, forcing people living below them to evacuate, and houses and commerical buildings collapsed or caught fire. Damage from the 1971 quake. Among those attending, in addition to Division personnel, were representatives from the California Institute of Technology, the U S. Geological Survey, the National Ocean Survey (a part of the National Oceanic and Atmospheric Administration), the University of California at Santa Barbara, the University of Southern California, California State College at Los Angeles, and the University of Washington; from several state agencies-the Division of Oil and Gas, the Division of Highways, the Department of Water Resources; from Los Angeles County and from Los Angeles City; as well as from several private consulting firms. 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. Landslides that were documented in the late 1980s, the damage was enormous variously. 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