[20], 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. 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. Had shaking of the endangered reservoirs continued for 2 seconds more, it has been estimated that there would have been no time to evacuate those below. Full Record The 1971 San Fernando (a.k.a. The event affected a number of health-care facilities in Sylmar, San Fernando, and other densely populated areas north of central Los Angeles. February 9, 1971, Granada Hills, CA. The largest cumulative amount of slip of 6 feet 7 inches (2.01 m) occurred along the Sylmar and Tujunga segments. The overall fault displacement was summarized by geologist Barclay Kamb and others as "nearly equal amounts of north–south compression, vertical uplift (north side up), and left lateral slip and hence may be described as a thrusting of a northern block to the southwest over a southern block, along a fault surface dipping about 45° north. 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 unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. [8], Paleomagnetic evidence has shown that the western Transverse Ranges were formed as the Pacific Plate moved northward relative to the North American Plate. The earthquake was not, or should not have been, unexpected. Sylmar, Los Angeles 1971 San Fernando earthquake Antelope Valley Emergency! osti.gov technical report: damage survey, san fernando earthquake of february 9, 1971. Loss of life that was directly attributable to the earthquake amounted to 58 (a number of heart attack and other health-related deaths were not included in this figure). 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. Accentuated damage near alluvium had been documented during the investigation of the effects of the 1969 Santa Rosa earthquakes. 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. … Because of its consequences, the San Fernando earthquake was a major earthquake from the engineering point of view, even though it was only a moderate shock in seismological terms. 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. 8 x 10 in. The landslides they mapped included those in the eastern half of the San Fernando quadrangle. 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. [20], Both the Upper and Lower Van Norman dams were severely damaged as a result of the earthquake. 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. 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 San Fernando earthquake has been extensively studied by many seismologists, geologists, and earthquake engineers. 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. • The epicenter of the magnitude 6.6 disastrous earthquake was in the foothills of the San Gabriel Mountains, at the northeastern edge of the Valley. Part of the reason there were so many stations to capture the event was a 1965 ordinance that required newly constructed buildings in Beverly Hills and Los Angeles over six stories in height to be outfitted with three of the instruments. The estimate for repairs at the site was $485,000. Northridge, CA Earthquake 1994 - Miscellaneous Pictures - … The southern California soil shook violently the morning of February 9, 1971. Two were due to power failure of life-support systems and one, that of an employee who was struck by part of the collapsing building as he or she tried to exit the building, was a direct result of the destruction. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. 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. Black and white photograph. More than 400 portable classrooms and 53 wood frame pre-Field Act buildings were also in use. In addition to the collapse of the stairways, the elevators were out of commission. 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 upstream slope of Lower San Fernando Dam failed during the 1971 San Fernando earthquake (Seed et al. 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. The event was one in a series that affected the Los Angeles area in the late … One of the hardest-hit buildings was the just-completed San Fernando Veterans Administration Hospital, whose unreinforced concrete wings collapsed, killing at … 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. 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 measured at 6.6 at its epicenter. The success in this area spurred the initiation of California's Strong Motion Instrumentation Program. A little known fact was that the Van Norman … 100% satisfaction guaranteed. The maximum slip was up to 2 meters (6 feet). 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. 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… Title: DAMAGE SURVEY, SAN FERNANDO EARTHQUAKE OF FEBRUARY 9, 1971. An inspection of the lower dam in 1964 paved the way towards an arrangement between the State of California and the Los Angeles Department of Water and Power that would maintain the reservoir's water level that was reduced 10 feet lower than was typical. Damage from the San Fernando Earthquake of 1971 was mostly to freeway overpasses and hospitals. While lateral, transverse, and vertical motions were all observed, the largest individual component of movement was 5 ft 3 in (1.60 m) of left lateral slip near the middle of the Sylmar segment. The area of surface breaks on the ground at the site was 900 ft (270 m) (at its widest) and stretched 4,000 ft (1,200 m) down a 1% grade slope towards the southwest. The duration of strong ground motion at that location was probably similar to the 12 seconds observed at the Pacoima Dam, and it is thought that another few seconds' shaking might have been enough to bring the building to collapse. [23], While the Newhall Pass interchange was still under construction at the time of the earthquake, the requisite components of the overpass were complete. 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. 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 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). 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. No need to register, buy now! The epicenter was located approximately 10 km northeast of LSFD at … 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. The complete structure, including the four external staircases, could be considered five separate buildings, because the stair towers were detached from the main building by about four inches. Scarps ran along the sidewalk and across the property. [15], In early 1971, the San Fernando Valley was the scene of a dense network of strong-motion seismometers, which provided a total of 241 seismograms. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information Transportation around the Los Angeles area was severely afflicted with roadway failures and the partial collapse of several major freeway interchanges. 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. Find art you love and shop high-quality art prints, photographs, framed artworks and posters at Art.com. 2. The gray zones represent areas with unsafe wood-frame dwellings (the locations of which are shown by a diamond symbols). 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. 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. San Fernando Earthquake ofFebruary 9, 1971, in the epicentral region on a mountainridge at Pacoima Dam ofthe Los Angeles County FloodCon­ trol District. 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. A preliminary report of their investigations is presented in this magazine. In the vicinity of the Sylmar Fault segment, there was a low possibility of landslides due to a lack of elevation change, but in the foothills and mountainous area a large amount of landsliding occurred and more work was necessary to eliminate the possibility of misidentifying a feature. Since the collapse of the dam lowered its overall height, the decision to reduce its capacity proved to be a valuable bit of insurance. [24], The large number of public school buildings in the Los Angeles area displayed mixed responses to the shaking, and those that were built after the enforcement of the Field Act clearly showed the results of the reformed construction styles. Apr 18, 2012 - Olive View Medical Center after the 1971 Sylmar Earthquake In the city of San Fernando, underground water, sewer, and gas systems suffered breaks too numerous to count, and some sections were so badly damaged that they were abandoned. The wood frame buildings (classrooms, a multipurpose building, and some bungalows) were built after the Field Act, and damage and cleanup costs there totaled $42,000. 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 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. [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. Charlie Bishop came from San Francisco, as well as several staff members from Sacramento-Quint Aune, Chief Wes Bruer, Bob Matthews, and Bennie Troxel. 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. Damage to the building, including ceiling tiles, telephone equipment, and elevator doors, was excessive at the basement and the first floor, with little damage further up. Damage from the 1971 quake. [21], The upper dam was constructed in 1921 with the hydraulic fill process, three years after the larger lower dam, which was fabricated using the same style. 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. 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 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. 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. Gordon Oakeshott, Deputy Chief had mapped part of the San Fernando 15-minute quadrangle in doing research for his doctoral dissertation in 1936; he revised and extended the map for publication in 1958 as California Division of Mines Bulletin 172, Geology and mineral deposits of the San Fernando quadrangle, Los Angeles County, California. The damaged buildings variously were wood-frame and masonry structures. The death toll of this earthquake was about 58, but the property damage was enormous. Earthquake bracing used in the building's second through fifth floors consisted of shear walls, but a rarely used slip joint technique used with the concrete walls at the first floor kept them from being part of that system. The 1971 San Fernando Earthquake. Olive View Hospital, a county-owned structure, is such a lesson. 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. Intact blocks of embankment material moved tens of feet on liquefied hydraulic fill shell material (figures D-8-1 and D-8-2). The hospital was severely damaged six weeks after it opened during the 6.5–6.7 1971 San Fernando earthquake (February 9, 1971), which caused the collapse of the four stairwell wings, as well as the parking structure. One unit would be installed within the structure and the second would be set up as a free-field unit located a short distance away from the facility. 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. Shear cracking occurred at the column closest to the western abutment, and the ground at the same column's base exhibited evidence of rotation. 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. Messrs. Gray and Caldwell went immediately to the Los Angeles District Office where they maintained constant contact with field, administrative, and disaster staffs. 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. 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