[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. 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). 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. The 1971 San Fernando (a.k.a. [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. 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 success in this area spurred the initiation of California's Strong Motion Instrumentation Program. A little known fact was that the Van Norman … This stipulation ultimately found its way into the Uniform Building Code as an appendix several years later. As a result, building of new structures for human occupancy across active fault lines was banned. 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. 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. 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. 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. Uplift and other effects affected private homes and businesses. 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 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 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. The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. The San Bernardino, Santa Ynez, and Santa Monica Mountains are also part of the anomalous east–west trending Transverse Ranges. 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 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. Full Record The hospital was staffed by 98 employees and had 606 patients at the time of the earthquake; all three deaths that occurred at the Olive View complex were in this building. [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. February 9, 1971, Granada Hills, CA. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. 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 Earthquake Collapsed Freeway Overpasses Photo. The structure had been built according to earthquake-resistant code provisions; mapped faults, as shown by Dr. Oakeshott on his San Fernando quadrangle, were considered in the engineering design. Earthquake damage at the Olive View Hospital from the Sylmar earthquake of February 9, 1971. [20], Both the Upper and Lower Van Norman dams were severely damaged as a result of the earthquake. [17], The damage was greatest near and well north of the surface faulting, and at the foot of the mountains. 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. The act restricts construction of buildings designed for human occupancy across potentially active faults. More than 400 portable classrooms and 53 wood frame pre-Field Act buildings were also in use. Find the perfect san fernando earthquake 1971 stock photo. 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… 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. The 1971 San Fernando earthquake struck at 6:00:55 a.m. PST on the morning of February 9, 1971. There are various names for this earthquake. 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. 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. The maximum slip was up to 2 meters (6 feet). 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. Soil liquefaction played a role within confined areas of the slide, but it was not responsible for all the motion at the site, and tectonic slip of faults in the area was also excluded as a cause. [12], In repeated measurements of the different fault breaks, the results remained consistent, leading to the belief that most of the slip had occurred during the mainshock. The damaged buildings variously were wood-frame and masonry structures. 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 1971 earthquake has enabled him to add another facet to the study of the area he now knows so well. 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. 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. 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. [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. [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. [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. [25], Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. The landslides they mapped included those in the eastern half of the San Fernando quadrangle. [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. It was an expensive and heartbreaking lesson, but California has learned something, and can take heart. [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). The group of one-story structures 300 feet west of the new facility, and some other buildings, were not damaged. These buildings suffered the most damage, with four buildings totally collapsing, which resulted in a large loss of life at the facility. 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. 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. 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. The narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion. 8 x 10 in. Find art you love and shop high-quality art prints, photographs, framed artworks and posters at Art.com. 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. 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. Damage from the San Fernando, 1971, earthquake. As one portion of the study, Dick Saul mapped in detail the southeast quarter of the Oat Mountain 71/2-minute quadrangle, through which the Santa Susana thrust fault cuts obliquely. 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. Besides those credited as authors, virtually all staff members in the Los Angeles office participated in the study: Wilma Ashby, Pat Caldwell, George Cleveland, Bill Edgington, Jim Evans, Don Fife, Cathy Govaller, Cliff Gray, Ed Kiessling, and Paul Morton. It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized." 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 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. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. The upper lake subsided 3 feet (0.91 m) and was displaced about 5 feet (1.5 m) as a result of the ground movement, and the dam's concrete lining cracked and slumped. Most of the masonry and reinforced concrete buildings constructed after 1933 withstood the shaking and most did not collapse, but in 1972 a resolution came forth to abandon the site and the remaining structures were later demolished, the site becoming a city park. 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. [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.

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