[6] The origin of faulting was located five miles north of the San Fernando Valley. Dr. Thomas Heaton, the director of Caltech’s Earthquake Engineering Research Laboratory, breaks it down. My dad rushed us out and filmed some of the freeway damage. 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 Sylmar quake, as it’s known — which is one of the strongest earthquakes recorded in Southern California history — killed 65 people, injured 2,000 more, and caused north of $500 million in property damage, according to the California Institute of Technology (Caltech). 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. 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. These buildings suffered the most damage, with four buildings totally collapsing, which resulted in a large loss of life at the facility. Nursing homes also were affected. 2). The San Fernando earthquake — like virtually all earthquakes — was caused by sudden displacement of rock masses along a fault. [14], 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. There was a brand new hospital, the Olive View Hospital, that had just been completed, and they were just staffing it up, and it collapsed in the earthquake. [10], Paleomagnetic evidence has shown that the western Transverse Ranges were formed as the Pacific Plate moved northward relative to the North American Plate. [28], Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. 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). Download it here. We sat down with the Director of Caltech’s Earthquake Engineering Research Laboratory and Professor Emeritus of Engineering Seismology, Dr. Thomas Heaton, to better understand what happened 50 years ago, what we learned from it, and how we can better alert the public. [26], While the Newhall Pass interchange was still under construction at the time of the earthquake, the requisite components of the overpass were complete. 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. Get the best experience and stay connected to your community with our Spectrum News app. The unincorporated districts of Newhall, Saugus, and Solemint Junction had moderate damage, even to newer buildings. 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 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. [18], 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. 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). But fixing your walls is nothing compared to losing the house. This stipulation ultimately found its way into the Uniform Building Code as an appendix several years later. (AP Photo). The 1971 San Fernando, or Sylmar, earthquake was the worst to hit an urban area of California since the 1933 magnitude-6.4 Long Beach quake. 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. At 6 o’clock in the morning on February 9, 1971, the reservoir keeper of the Lower Van Norman Dam in Southern California tried to get out of bed. 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 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. [23], 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. Our new Spectrum News app is the most convenient way to get the stories that matter to you. State and local agencies (as well as the property owner) were then responsible for enforcing or complying with the building restrictions. 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. Also often known as the San Fernando earthquake, the Feb. 8, 1971, magnitude-6.5 quake occurred on a Tuesday at about 6:01 a.m. Its origin was in the … Author irememberjfk_l6fq3c Posted on July 10, 2019 Categories The News. 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. A magnitude-6.6 earthquake was shaking his home nestled at the bottom of the dam. One of the hardest-hit buildings was the just-completed San Fernando Veterans Administration Hospital, whose unreinforced concrete wings collapsed, killing at … 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. [22], The Veterans Administration Hospital entered into service as a tuberculosis hospital in 1926 and became a general hospital in the 1960s. The two blue lines mark the faults which ruptured in the San Fernando earthquake 46 years ago today. The total surface rupture was roughly 19 km (12 miles) long. [23], Both the Upper and Lower Van Norman dams were severely damaged as a result of the earthquake. Even if you recorded them, you couldn’t read them. Next week marks 50 years since the 1971 San Fernando earthquake. “The San Fernando earthquake led to more policy changes than probably any other earthquake that we’ve had,” says Dr. Lucy Jones, a Southern California-based seismologist and author . 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. Fortunately, there was six feet. The Los Angeles Department of Water and Power, as well as the County of Los Angeles, investigated and verified that local soil conditions contributed to the ground displacement and resulting destruction. It's called hydraulic fill, a kind of mining they used to do. So in the '80s, I was with the U.S. Geological Survey, and I was trying to push our office in Caltech towards having better systems to react during the earthquake itself. To learn more about protecting your house, go to StrengthenMyHouse.com. The magnitude 6.6 earthquake left 65 dead; injured another 2,000 people and caused half a billion dollars in damage (about $3.2 billion today). 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. The accelerometer was mounted on a concrete platform on a granite ridge just above one of the arch dam's abutments. Fifty years ago today, February 9, 1971, occurred the deadly and devastating San Fernando Earthquake, aka the Sylmar Quake. Tuesday marks 50 years since the 1971 Sylmar-San Fernando earthquake unleashed its fury on Los Angeles just after 6 a.m. [21], 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. But I think it's got another couple of decades before the owners have to actually retrofit these things. 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. Known as the San Fernando earthquake or the Sylmar earthquake, it caused 58 deaths and more than $500 million in damage. Bryant, his 13-year-old daughter, Gianna, and six other passengers were flying from Orange County to a youth basketball tournament at his Mamba Sports Academy in Ventura County on Jan. 26, 2020, when the helicopter encountered thick fog in the San Fernando Valley north of Los Angeles. 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. Hospital employees from 1971 remember earthquake Share this: ... including three at Olive View and 49 at the Veterans Administration Hospital in San Fernando – injured 2,000 and caused … The Olive View Medical Center and Veterans Hospital both experienced very heavy damage, and buildings collapsed at both sites, causing the majority of deaths that occurred. The San Fernando earthquake, or Sylmar quake as it’s also called, killed 64 people, injured thousands more, and caused more than $500 million worth of damage. [11], The San Fernando earthquake occurred on February 9, 1971, at 6:00:41 am Pacific Standard Time (14:00:41 UTC) with a strong ground motion duration of about 12 seconds as recorded by seismometers,[12] although the whole event was reported to have lasted about 60 seconds. With a moment magnitude of 6.7, the Northridge earthquake was the strongest earthquake to strike the Los Angeles area since the 1971 San Fernando earthquake, which also had a magnitude of 6.7. The difference in rigidity at the second floor was proposed as a cause of the considerable damage to the lower levels. 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 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. This story actually starts in San Fernando. So when an earthquake comes along, it's going to give you a big enough load that you have to fix all your walls. From left: Duane L. Georgeson, Jules Bergman examine damage in the aftermath of the Sylmar Earthquake / 1971 San Fernando earthquake, in the Walt Disney Television via Getty Images / … They’re one story tall, no windows, just solid concrete walls. [22], The Medical Treatment and Care Building included a basement that was exposed (above grade) on the east and south sides, mixed (above and below grade) on the west side, and below grade on the north side of the building, the variation being due to the shallow slope at the site. [24], 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). 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. So the things that matter the most are very rare, and you have no idea when the next one's going to be. And of course it met all the codes at that time, it was a hospital. 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. The damaged buildings variously were wood-frame and masonry structures. The seismologists would look at records that came in on telephone lines and in the [San Fernando] earthquake, the telephone lines were knocked out, and even more so, all of the records were off-scale anyway. 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. 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. Twenty-six buildings that were built prior to 1933 had been constructed following the local building codes and did not require seismic-resistant designs. 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 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. 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 greatest number of slides were centered to the southwest of the mainshock epicenter and close to the areas where surface faulting took place. But the lessons learned from the great 1971 San Fernando earthquake remained strictly a local education. [30], 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. Shaking from the M6.5 quake caused a hospital to collapse, killing dozens of people. 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 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. 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 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. Fifty years ago this week, the deadly Sylmar earthquake rattled Southern California, leaving dozens of people dead and causing more than $500 million in property damage. The estimate for repairs at the site was $485,000. But the Sylmar quake steered the Southern California region into implementing new and safer building codes to enhance public safety, advanced earthquake technology, and, according to Caltech, led to a coalition of the United States Geological Survey (USGS) and the university in expanding seismic monitoring through the region. Scarps ran along the sidewalk and across the property. 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. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. The success in this area spurred the initiation of California's Strong Motion Instrumentation Program. [27], 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. 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 red line is the fault on which the Northridge quake occurred in 1994. ... where it caused huge damage to the old Olive View Hospital. 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. By the late 1980s, the program had instrumented more than 450 structures, bridges, dams, and power plants. [13], 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. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. If that fault ever duplicates its great 1811 quake (which caused the great river to flow backwards), look for the possible deaths of millions. ... known as the San Fernando or Sylmar Earthquake. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. [24], 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. 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. Afterwards, they told people you have to put a hook in the rebar so that you positively connect the rebar from the column to the rebar from the beam. 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 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. Abundant cracks formed in the ground at the site, and some foundations and many sidewalks were also cracked. And it turns out that about 40 feet of the top of the dam slid in, and there was a six-foot leeway left to hold back the water. The largest cumulative amount of slip of 6 feet 7 inches (2.01 m) occurred along the Sylmar and Tujunga segments. And it's not going to be easy, it's expensive and the people who are in the buildings often have no idea they are in a dangerous building. 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 fix had to do not so much with changing the concrete or the steel, but the way they connect all the steel together inside the concrete. 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. They're short. 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. 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. 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. This made the earthquake the most documented event, at the time, in terms of strong-motion seismology; by comparison, the 1964 Alaska earthquake did not provide any strong motion records. 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. EL SEGUNDO, Calif. â€” At 6 a.m. on February 9, 1971, a 6.6-magnitude earthquake struck the San Fernando Valley. The statistics of earthquakes are very much like, believe it or not, epidemics and pandemics. 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. [22], On the grounds, there were cracks in the pavement and soil, but no surface faulting. The event affected a number of health-care facilities in Sylmar, San Fernando, and other densely populated areas north of central Los Angeles. They just take a fire hose on a Hillside and slurry the mud into someplace and let it settle, but it doesn't make a very stable slope. 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. Considerable damage was seen in localized portions of the valley and also in the foothills of the San Gabriel Mountains above the fault block. Some canals in the area of the dams were damaged and not usable, and dikes experienced slumping but these did not present a hazard. [27], 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. Few of the slides that were logged from the air were also observed from the ground. 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. The San Bernardino, Santa Ynez, and Santa Monica Mountains are also part of the anomalous east–west trending Transverse Ranges. The 1971 San Fernando, or Sylmar, earthquake was the worst to hit an urban area of California since the 1933 magnitude-6.4 Long Beach quake. You can look at some statistics, and the statistics are something we call a Pareto distribution, which means that the biggest events, biggest earthquakes, biggest pandemics are the ones that really matter, and they don't happen very often. Accentuated damage near alluvium had been documented during the investigation of the effects of the 1969 Santa Rosa earthquakes. The act restricts construction of buildings designed for human occupancy across potentially active faults. Several landslides occurred between Balboa Boulevard and California State Route 14, but the most significant damage occurred at the two major interchanges.
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