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. The unanticipated thrust earthquake had a magnitude of 6.5 on the Ms scale, and a maximum Mercalli intensity of XI (Extreme). 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. The 1971 earthquake has enabled him to add another facet to the study of the area he now knows so well. 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). 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. 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. From Wikipedia: 1971 Quake. • 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. These buildings suffered the most damage, with four buildings totally collapsing, which resulted in a large loss of life at the facility. [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 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. 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. 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. Following the San Fernando event, earthquake engineers and seismologists from established scientific organizations, as well as the newly formed Los Angeles County Earthquake Commission, stated their recommendations that were based on the lessons learned. 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. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information 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. [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. 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. Title: DAMAGE SURVEY, SAN FERNANDO EARTHQUAKE OF FEBRUARY 9, 1971. 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 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. [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 greatest number of slides were centered to the southwest of the mainshock epicenter and close to the areas where surface faulting took place. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. Unlike the situation at the Antelope Valley Interchange, permanent ground movement (defined as several inches of left-lateral displacement with possibly an element of thrusting) was observed in the area. Find the perfect san fernando earthquake 1971 stock photo. 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. 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. As the plate shifted to the north, a portion of the terrane that was once parallel with the coast was rotated in a clockwise manner, which left it positioned in its east–west orientation. 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. They paid particular attention to hillsides that might give way in aftershocks, causing more havoc than already existed. In 1962, the Division inaugurated a study of the frontal fault system along 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. Charlie Bishop came from San Francisco, as well as several staff members from Sacramento-Quint Aune, Chief Wes Bruer, Bob Matthews, and Bennie Troxel. This paper compares the distribution of damage from the San Fernando, 1971, and Northridge, 1994, earthquakes. The five-story, reinforced-concrete Medical Treatment and Care Building was one of three new additions to the complex (all three of which sustained damage), was assembled with earthquake-resistant construction techniques, and was completed in December 1970. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. 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. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. [8], Paleomagnetic evidence has shown that the western Transverse Ranges were formed as the Pacific Plate moved northward relative to the North American Plate. When the Sylmar-San Fernando earthquake struck Southern California in 1971, 64 people were killed and more than 2,500 injured. 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. In the southern California area--from Point Arguello to Nevada and from the Mexican border to Owens Valley--seismic records suggest that 37 shocks of this magnitude or greater might be expected in a century; indeed, one might expect two shocks with a magnitude of 8.0 or more. The estimate for repairs at the site was $485,000. The event was one in a series that affected the Los Angeles area in the late … The 1979 Imperial Valley and 1987 Whittier Narrows earthquakes were presented as gainful events that were recorded during that period, because both produced valuable data that increased knowledge of how moderate events affect buildings. The southern California soil shook violently the morning of February 9, 1971. Sylmar, Los Angeles 1971 San Fernando earthquake Antelope Valley Emergency! Some canals in the area of the dams were damaged and not usable, and dikes experienced slumping but these did not present a hazard. Intact blocks of embankment material moved tens of feet on liquefied hydraulic fill shell material (figures D-8-1 and D-8-2). [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. By the late 1980s, the program had instrumented more than 450 structures, bridges, dams, and power plants. 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. The 1971 San Fernando earthquake struck at 6:00:55 a.m. PST on the morning of February 9, 1971. This was done as a precaution to accommodate further collapse due to a strong aftershock. 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. Most deaths occurred at the Veterans and Olive View hospital complexes, and the rest were located at private residences, the highway overpass collapses, and a ceiling collapse at the Midnight Mission in downtown Los Angeles. 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. Earthquake damage at the Olive View Hospital from the Sylmar earthquake of February 9, 1971. San Fernando Earthquake ofFebruary 9, 1971, in the epicentral region on a mountainridge at Pacoima Dam ofthe Los Angeles County FloodCon­ trol District. 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 narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion. 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. "[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 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. 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. 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. 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. [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. [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. 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. 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 San Fernando earthquake has been extensively studied by many seismologists, geologists, and earthquake engineers. [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. 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. 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. [12][13], All segments shared the common elements of thrust faulting with a component of left-lateral slip, a general east–west strike and a northward dip, but they were not unified with regard to their connection to the associated underlying bedrock. 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