1971 san fernando earthquake damage

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). 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. [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 no movement on the faults near the hospital; damage to the building has been attributed to the intense shaking to which it was subjected. 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. 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. 1975). 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. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. 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. 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. 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. 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 … 2. The 1971 earthquake has enabled him to add another facet to the study of the area he now knows so well. Twenty-six buildings that were built prior to 1933 had been constructed following the local building codes and did not require seismic-resistant designs. 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. 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. On February 9th, 1971, at approximately 6:00am, the foothills of the San Gabriel Mountains were struck by a 6.7 earthquake. 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 damage at the lower dam consisted of a landslide that dislocated a section of the embankment. [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 act restricts construction of buildings designed for human occupancy across potentially active faults. The fault that was responsible for the movement was not one that had been considered a threat, and this highlighted the urgency to identify other similar faults in the Los Angeles metropolitan area. Since both occurred in urban and industrial areas and resulted in significant economic impairment, each event drew critical observation from planning authorities, and has been thoroughly studied in the scientific communities. This destructive earthquake occurred in a sparsely populated area of the San Gabriel Mountains, near San Fernando. 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. 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 landslides they mapped included those in the eastern half of the San Fernando quadrangle. As a result, building of new structures for human occupancy across active fault lines was banned. [27], California Strong Motion Instrumentation Program, Prior to the San Fernando earthquake, some structural engineers had already believed that the existing groundwork for seismic design required enhancement. A state of emergency in California after the most serious earthquake since the San … 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 Uplift and other effects affected private homes and businesses. 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. 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. Electrical power and communications failed at the hospital at the time of the earthquake, but very few people occupied the lower floors and the stairways at the early hour. We must hurry to learn what we can, and to put to use what we know, while our luck holds.... M.R.H. 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. Intact blocks of embankment material moved tens of feet on liquefied hydraulic fill shell material (figures D-8-1 and D-8-2). The main building was demolished at a cost of $127,000, and none of the various post-Field Act buildings were damaged at the site. 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. 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. This was done as a precaution to accommodate further collapse due to a strong aftershock. 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. The unanticipated thrust earthquake had a magnitude of 6.5 on the Ms scale, and a maximum Mercalli intensity of XI (Extreme). From Wikipedia: 1971 Quake. [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. 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. San Fernando earthquake Sylmar 6.6 Richter scale 1971 damage collapse building parking structure emergency temblor shake crack Major damage was concentrated at the Newhall Pass Interchange, which was under construction at the time of the 1971 San Fernando earthquake in Southern California. 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. Shear cracking occurred at the column closest to the western abutment, and the ground at the same column's base exhibited evidence of rotation. Since the collapse of the dam lowered its overall height, the decision to reduce its capacity proved to be a valuable bit of insurance. The earthquake that rocked the northern San Fernando Valley, near Sylmar measured magnitude 6.6 on the Richter magnitude scale. [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. The estimate for repairs at the site was $485,000. By the late 1980s, the program had instrumented more than 450 structures, bridges, dams, and power plants. The frontal fault system at the base of the San Gabriel Mountains extends from the San Jacinto Fault Zone in the east to offshore Malibu in the west, and is defined primarily by moderate to shallow north-dipping faults, with a conservative vertical displacement estimated at 4,000–5,000 feet (1,200–1,500 m). The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. Transportation around the Los Angeles area was severely afflicted with roadway failures and the partial collapse of several major freeway interchanges. February 9, 1971, Granada Hills, CA. 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. 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. 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. [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. In addition to the collapse of the stairways, the elevators were out of commission. Sylmar) earthquake (Mw = 6.6) occurred in the early morning hours of February 9. Northridge, CA Earthquake 1994 - Miscellaneous Pictures - … Considerable damage was seen in localized portions of the valley and also in the foothills of the San Gabriel Mountains above the fault block. 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. 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. The California Division of Mines and Geology is continuing to act as an information exchange center for those who have been and are engaged in geologic, se is mo logic, and geodetic investigations of the earthquake. 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. 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 maximum slip was up to 2 meters (6 feet). "[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. 100% satisfaction guaranteed. 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. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. There are various names for this earthquake. 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. [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. [17], The damage was greatest near and well north of the surface faulting, and at the foot of the mountains. 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. The domain of the ranges stretches from the Channel Islands offshore, to the Little San Bernardino Mountains, 300 miles (480 km) to the east. Service breaks, main breaks and shattered mains in the water pipe system are shown, respectively, by solid points, and by small and large open circles. Abundant cracks formed in the ground at the site, and some foundations and many sidewalks were also cracked. The San Bernardino, Santa Ynez, and Santa Monica Mountains are also part of the anomalous east–west trending Transverse Ranges. But what we have learned is far surpassed by our astonishing luck. One of the hardest-hit buildings was the just-completed San Fernando Veterans Administration Hospital, whose unreinforced concrete wings collapsed, killing at … The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. Casualties in these highly affected areas might have increased had the shock occurred later in the day. 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. Schools were affected, as they had been during the 1933 Long Beach earthquake, but this time amended construction styles improved the outcome for the thousands of school buildings in the Los Angeles area. [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). 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. Peter Fischer, of Whittier College, had the foresight and was instrumental in making arrangements for Marine Corps support. 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. The epicenter was located approximately 10 km northeast of LSFD at … [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 accelerometer was mounted on a concrete platform on a granite ridge just above one of the arch dam's abutments. The success in this area spurred the initiation of California's Strong Motion Instrumentation Program. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information It is evident, however, that more faults in the San Fernando Valley area may be active today than are now recognized." 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. Nursing homes also were affected. 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. [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. These buildings suffered the most damage, with four buildings totally collapsing, which resulted in a large loss of life at the facility. 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. When the Sylmar-San Fernando earthquake struck Southern California in 1971, 64 people were killed and more than 2,500 injured. San Fernando, CA Earthquake 1971 – Olive View Hospital Photos, Residental House Collapse. 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. 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 hospital buildings, the freeway overpasses, and the Sylmar Juvenile Hall were on coarse alluvium that overlay thousands of feet of loosely consolidated sedimentary material. 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. The most frequently-encountered type of slide was the surficial (less than 3 feet (0.91 m) thick) debris slides and were most often encountered on terrain consisting of sedimentary rock. The Antelope Valley Freeway had damage from Newhall Pass to the northeast, primarily from settling and alignment issues, as well as splintering and cracking at the Santa Clara River and Solemint bridges. Recordprocessed by the JetPropulsion Laboratory, Pasadena; made avail able by the Earthquake Engineering Research Laboratory, California In 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. The difference in rigidity at the second floor was proposed as a cause of the considerable damage to the lower levels. 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. The origin of faulting was located five miles north of the San Fernando Valley. Only three lives were lost: two were patients who died when forcibly cut off from their positive pressure breathing equipment, and one staff member was killed by falling debris outside the building. Few of the slides that were logged from the air were also observed from the ground. [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 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. [19], The Veterans Administration Hospital entered into service as a tuberculosis hospital in 1926 and became a general hospital in the 1960s. State and local agencies (as well as the property owner) were then responsible for enforcing or complying with the building restrictions. 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. [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. [28][29], 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. 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. A little known fact was that the Van Norman … 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 1971 San Fernando earthquake with a 6.6 magnitude and large aftershocks caused over $500 million in damages and destruction to infrastructure; including the collapsed freeway overpasses on the Interstate freeways 5, 14, and 210, destruction of several hospitals in the North Los Angeles area, and damage to the Van Norman Dam in Granada Hills. 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. The earthquake was generated by thrust faulting on the Sierra Madre fault. • 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. [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. Sylmar, Los Angeles 1971 San Fernando earthquake Antelope Valley Emergency! … They were supported by aircraft: a fixed wing chartered plane and a helicopter provided and manned by the U. S. Marine Corps. The event was one in a series that affected the Los Angeles area in the late … 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. 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. 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. 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. 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. 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