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. 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. 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. 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. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. The maximum slip was up to 2 meters (6 feet). San Fernando Earthquake ofFebruary 9, 1971, in the epicentral region on a mountainridge at Pacoima Dam ofthe Los Angeles County FloodCon­ trol District. 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. On the day following the earthquake, State Geologist Wesley Bruer convened a meeting of more than 40 geologists and seismologists engaged in studying the earthquake, so that all investigative activities might be coordinated. They paid particular attention to hillsides that might give way in aftershocks, causing more havoc than already existed. 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 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. Three Division geologists had an especial interest in the area, as well as especial expertise. [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. 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 unanticipated thrust earthquake had a magnitude of 6.5 on the Ms scale, and a maximum Mercalli intensity of XI (Extreme). The upstream slope of Lower San Fernando Dam failed during the 1971 San Fernando earthquake (Seed et al. Damage from the San Fernando Earthquake of 1971 was mostly to freeway overpasses and hospitals. The difference in rigidity at the second floor was proposed as a cause of the considerable damage to the lower levels. Few of the slides that were logged from the air were also observed from the ground. The earthquake that rocked the northern San Fernando Valley, near Sylmar measured magnitude 6.6 on the Richter magnitude scale. 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. 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. 1975). 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. It was an expensive and heartbreaking lesson, but California has learned something, and can take heart. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. [25], Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. 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 death toll of this earthquake was about 58, but the property damage was enormous. Abundant cracks formed in the ground at the site, and some foundations and many sidewalks were also cracked. 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. [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. 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. [22], 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. 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 (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. 1971 2/09 14:01 UTC 34.40N 118.39W 5km deep Ms=6.5, San Fernando, California. The earthquake was generated by thrust faulting on the Sierra Madre fault. The origin of faulting was located five miles north of the San Fernando Valley. Sylmar) earthquake (Mw = 6.6) occurred in the early morning hours of February 9. [17], The damage was greatest near and well north of the surface faulting, and at the foot of the mountains. It was California's third worst earthquake in terms of lives lost (exceeded by San Francisco, 1906 and Long Beach, 1933) and second in terms of property damage (exceeded by San Francisco, 1906). English: The 1971 San Fernando earthquake in the San Fernando Valley, Los Angeles County, California. 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 gray zones represent areas with unsafe wood-frame dwellings (the locations of which are shown by a diamond symbols). There are various names for this earthquake. Scarps ran along the sidewalk and across the property. [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 main building was demolished at a cost of $127,000, and none of the various post-Field Act buildings were damaged at the site. [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. The epicenter was located approximately 10 km northeast of LSFD at … This destructive earthquake occurred in a sparsely populated area of the San Gabriel Mountains, near San Fernando. 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. 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 Indian Hills Medical Center, the Foothill Medical Building, and the Pacoima Lutheran Professional building were heavily damaged. Earthquake Damage Earthquake And Tsunami California History Southern California Vintage California San Andreas Fault San Francisco Earthquake San Fernando Valley Local History 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. 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. [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. 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 … 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. 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. This early and continuing exchange has added significantly to the effectiveness of the investigations. The Transverse Ranges form the perimeter of a series of basins that begins with the Santa Barbara Channel on the west end. [19], On the grounds, there were cracks in the pavement and soil, but no surface faulting. 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. State and local agencies (as well as the property owner) were then responsible for enforcing or complying with the building restrictions. Earthquake damage at Olive View Hospital, Sylmar, 1971 Creator Unknown Date Created and/or Issued 1971-02 2001-08-27 Publication Information California State University, Northridge. 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. 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. 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. 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 San Fernando earthquake has been extensively studied by many seismologists, geologists, and earthquake engineers. [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. 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. San Fernando, CA Earthquake 1971 – Olive View Hospital Photos, Residental House Collapse. Find the perfect san fernando earthquake 1971 stock photo. Northridge, CA Earthquake 1994 - Miscellaneous Pictures - … 2. Uplift and other effects affected private homes and businesses. 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. The narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion. 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. Olive View Hospital, a county-owned structure, is such a lesson. • 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. We must hurry to learn what we can, and to put to use what we know, while our luck holds.... M.R.H. 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. The act restricts construction of buildings designed for human occupancy across potentially active faults. 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 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 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. 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. University Library Contributing Institution California State University, Northridge Collection San Fernando Valley History Rights Information Later known as the San Fernando Earthquake, the quake was responsible for $500 million dollars worth of damage and causes 65 deaths (most of the deaths occurred when the Veteran's Administration Hospital collapsed). [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. 1971 San Fernando Earthquake Collapsed Freeway Overpasses Photo. 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. A preliminary report of their investigations is presented in this magazine. No need to register, buy now! 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. In 1962, the Division inaugurated a study of the frontal fault system along the San Gabriel Mountains. Some canals in the area of the dams were damaged and not usable, and dikes experienced slumping but these did not present a hazard. Twenty-six buildings that were built prior to 1933 had been constructed following the local building codes and did not require seismic-resistant designs. 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. Recordprocessed by the JetPropulsion Laboratory, Pasadena; made avail­ able by the Earthquake Engineering Research Laboratory, California In­ [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. 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. 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