1971 San Fernando earthquake

741: 1447: 1285: 1251: 1184: 750: 29: 1604: 1391:, as well as the County of Los Angeles, investigated and verified that local soil conditions contributed to the ground displacement and resulting destruction. 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. 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 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 1600:, the Seismic Hazards Mapping Act and Senate Bill 1953 (hospital safety requirements) were established. 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 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. New legislation included the Alquist-Priolo Special Studies Zone Act and the development of the Strong Motion Instrumentation Program. 772:. 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 landslides. 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 landslides occurred and more work was necessary to eliminate the possibility of misidentifying a feature. 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. 1578:(3.75 mi (6.04 km) from Pacoima Dam) were post-Field Act, one-story, wood construction. Abundant cracks formed in the ground at the site, and some foundations and many sidewalks were also cracked. The estimate for repairs at the site was $ 485,000. 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. 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. Gas lines were broken and separation of the buildings' porches was due to lateral displacement of up to six inches. 1726: 1293:

found to have occurred as a result of the shaking and not from ground displacement or faulting. Twenty-six buildings that were built prior to 1933 had been constructed following the local building codes and did not require seismic-resistant designs. These buildings suffered the most damage, with four buildings totally collapsing, which resulted in a large loss of life at the facility. 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.

657: 1712: 1479: 44: 1338: 1129:'s abutments. 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. 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. 539:, but this time amended construction styles improved the outcome for the thousands of school buildings in the Los Angeles area. Another result of the event involved the hundreds of various types of landslides that were documented in the San Gabriel Mountains. 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. 1698: 177: 1356:

Some canals in the area of the dams were damaged and not usable, and dikes experienced slumping but these did not present a hazard. The damage at the lower dam consisted of a landslide that dislocated a section of the embankment. 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 upper lake

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ground movement (defined as several inches of left-lateral displacement with possibly an element of thrusting) was observed in the area. 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

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floors and the stairways at the early hour. Casualties in these highly affected areas might have increased had the shock occurred later in the day. 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.

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both the initial shock and the aftershocks. Few of the slides that were logged from the air were also observed from the ground. The greatest number of slides were centered to the southwest of the mainshock epicenter and close to the areas where surface faulting took place. The slides ranged from 49–984 feet (15–300 m) in length, and could be further categorized as

1242:. The group of one-story structures 300 feet west of the new facility, and some other buildings, were not damaged. The damaged buildings variously were wood-frame and masonry structures. 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 1677:

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. By the late 1980s, the program had instrumented more than 450 structures, bridges, dams, and power plants. The

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and the associated brick veneer broke off and some fragments fell through the roof to a lower floor, while other material landed on an exit stairway and into a courtyard area. The main building was demolished at a cost of $ 127,000, and none of the various post-Field Act buildings were damaged at the

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and insufficient space (a 14 in (360 mm) seat was provided) on the support columns. 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

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technique used with the concrete walls at the first floor kept them from being part of that system. 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 difference in rigidity at

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that overlay thousands of feet of loosely consolidated sedimentary material. In the city of San Fernando, underground water, sewer, and gas systems suffered breaks too numerous to count, and some sections were so badly damaged that they were abandoned. Ground displacement damaged sidewalks and roads,

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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. The complete structure, including the four external staircases, could be considered

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and Veterans Hospital both experienced very heavy damage, and buildings collapsed at both sites, causing the majority of deaths that occurred. The buildings at both facilities were constructed with mixed styles, but engineers were unable to thoroughly study the buildings' responses because they were

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suffered varying degrees of damage, with four major facilities in the San Fernando Valley suffering structural damage, and two of those collapsing. The Indian Hills Medical Center, the Foothill Medical Building, and the Pacoima Lutheran Professional building were heavily damaged. Nursing homes also

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over 97 sq mi (250 km) of the mountainous areas north of the San Fernando Valley. Analysis revealed that the earthquake triggered over 1,000 landslides. Highly shattered rock was also documented along the ridge tops, and rockfalls (which continued for several days) were the result of

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duration of about 12 seconds as recorded by seismometers, although the whole event was reported to have lasted about 60 seconds. The origin of faulting was located five miles north of the San Fernando Valley. Considerable damage was seen in localized portions of the valley and also in the foothills

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at its high-risk sites. Other sites throughout the Los Angeles area had been instrumented as a result of local ordinances, and an unprecedented amount of strong motion data was recorded, more so than any other event up until that time. The success in this area spurred the initiation of California's

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were severely damaged as a result of the earthquake. 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. This was done as a precaution to accommodate further collapse due to a strong aftershock.

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techniques, and was completed in December 1970. 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. Two deaths were due to power failure of life-support systems and one employee

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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 success of the Imperial Valley event was especially pronounced because of a recently constructed and fully instrumented

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On the grounds, there were cracks in the pavement and soil, but no surface faulting. In addition to the collapse of the stairways, the elevators were out of commission. Electrical power and communications failed at the hospital at the time of the earthquake, but very few people occupied the lower

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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. The California Strong Motion Instrumentation

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as a result. 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. Unlike the situation at the Antelope Valley Interchange, permanent

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While the Newhall Pass interchange was still under construction at the time of the earthquake, the requisite components of the overpass were complete. 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

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The Veterans Administration Hospital entered into service as a tuberculosis hospital in 1926 and became a general hospital in the 1960s. 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

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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. As categorized during the intensive studies immediately following the earthquake, they were labeled the Mission Wells segment,

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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. Additional breaks occurred farther to the east that were in a more scattered fashion,

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pre-Field Act buildings were also in use. 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

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zones two and three. 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. One unit would be installed within the structure and the second would be set up as a

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were affected. 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. Scarps ran along the sidewalk and across the property. The building was not in use and remained standing. Though the reinforced

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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. While lateral, transverse, and vertical motions were all observed, the largest individual component of movement was 5 ft

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to the east. Loss of life that was directly attributable to the earthquake amounted to 58 (a number of heart attacks and other health-related deaths were not included in this figure). Most deaths occurred at the Veterans and Olive View hospital complexes, and the rest were located at private

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3 in (1.60 m) of left lateral slip near the middle of the Sylmar segment. The largest cumulative amount of slip of 6 feet 7 inches (2.01 m) occurred along the Sylmar and Tujunga segments. The overall fault displacement was summarized by geologist

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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. Several instances of failure or collapse at the site took place and two men were killed while driving in a

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the second floor was proposed as a cause of the considerable damage to the lower levels. 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.

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and others as "nearly equal amounts of north–south compression, vertical uplift (north side up), and left lateral slip and hence may be described as a thrusting of a northern block to the southwest over a southern block, along a fault surface dipping about 45°

1117:, a value that was twice as large as anything ever seen from an earthquake. 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. The 522:

Transportation around the Los Angeles area was severely afflicted with roadway failures and the partial collapse of several major freeway interchanges. All 4,084 square miles of Los Angeles County were declared a disaster area by California Governor

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occurred in 1994. 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.

1434:, but the most significant damage occurred at the two major interchanges. 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 1375:

that would maintain the reservoir's water level that was reduced 10 feet lower than was typical. Since the collapse of the dam lowered its overall height, the decision to reduce its capacity proved to be a valuable bit of insurance.

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clearly showed the results of the reformed construction styles. 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,

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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

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rupture, and creating regulatory zones around them called Earthquake Fault Zones. State and local agencies (as well as the property owner) were then responsible for enforcing or complying with the building restrictions.

1634:. Since it is presumed that surface rupture will likely take place where past surface displacement has occurred, the state geologist was given the responsibility for evaluating and mapping faults that had evidence of 1196:

with cracks in the more rigid asphalt and concrete often exceeding the width of the shift in the underlying soil. Accentuated damage near alluvium had been documented during the investigation of the effects of the

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requirements and exceeded what engineers had prepared for, and although most dwellings in the valley had been built in the prior two decades, even modern earthquake-resistant structures sustained serious damage.

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that was once parallel with the coast was rotated in a clockwise manner, which left it positioned in its east–west orientation. The Transverse Ranges form the perimeter of a series of basins that begins with the

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and surface faulting was extensive to the south of the epicenter in the mountains, as well as urban settings along city streets and neighborhoods. Uplift and other effects affected private homes and businesses.

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Gaudreau, É.; Hollingsworth, J.; Nissen, E.; Funning, G. (2022), "Complex 3-D surface deformation in the 1971 San Fernando, California earthquake reveals static and dynamic controls on off-fault deformation",

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as late as the 1960s. 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 0.5

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Prior to the San Fernando earthquake, some structural engineers had already believed that the existing groundwork for seismic design required enhancement. Although instruments had recorded a force of 0.33

1159:, and Solemint Junction had moderate damage, even to newer buildings. The area where the heaviest effects were present was limited by geographical features on the three remaining margins, with the 1191:

The damage was greatest near and well north of the surface faulting, and at the foot of the mountains. The hospital buildings, the freeway overpasses, and the Sylmar Juvenile Hall were on coarse

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five separate buildings, because the stair towers were detached from the main building by about four inches. Earthquake bracing used in the building's second through fifth floors consisted of

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The San Fernando, California, earthquake of February 9, 1971; a preliminary report published jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration

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The San Fernando, California, earthquake of February 9, 1971; a preliminary report published jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration

2190:

The San Fernando, California, earthquake of February 9, 1971; a preliminary report published jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration

2138:

The San Fernando, California, earthquake of February 9, 1971; a preliminary report published jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration

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The San Fernando, California, earthquake of February 9, 1971; a preliminary report published jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration

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process, three years after the larger lower dam, which was fabricated using the same style. An inspection of the lower dam in 1964 paved the way towards an arrangement between the

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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.

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free-field unit located a short distance away from the facility. As of 1973, a few of the highest risk (26 were completed in zone 3 alone) sites that had been completed were in

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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

1058:. 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 531:

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

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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.

691:. 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 3484: 2909: 2575: 1528:

A 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

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interchange in the south, where subsidence at the bridge approaches and cracking and buckling of the roadway made it unusable. Several landslides occurred between

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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.

707:, 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 2913: 628:, Red Mountain, Santa Susana, and Sierra Madre) all lining the north boundary. A small number of damaging events have occurred, with three in Santa Barbara ( 1470:

damaged. Shear cracking occurred at the column closest to the western abutment, and the ground at the same column's base exhibited evidence of rotation.

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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.

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The San Gabriel Mountains with the Veterans Hospital in center (above) and selected cities with reported felt intensity in the US (see intensity table)

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while the western portion of the most affected area had less pronounced scarps, especially the detached Mission Wells segment. Although the complete

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Following many of California's major earthquakes, lawmakers have acted quickly to develop legislation related to seismic safety. After the M6.4

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at their mouths. The narrow band of ground disturbances were found to have been the result of settling of the soft soil in a downhill motion.

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and Los Angeles over six stories in height to be outfitted with three of the instruments. This stipulation ultimately found its way into the

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that are bounded by the northern edge of the San Fernando Valley at the base of the San Gabriel Mountains. The unincorporated districts of

740: 511: 1847: 1843: 1183: 4306: 2903: 310: 43: 1238:–owned, 880-bed hospital complex had been built before the adoption of new construction techniques that had been put in place after the 3813: 2867: 749: 2918: 2885: 485:). The event was one in a series that affected Los Angeles county in the late 20th century. Damage was locally severe in the northern 3470: 1388: 1372: 1070:

In early 1971, the San Fernando Valley was the scene of a dense network of strong-motion seismometers, which provided a total of 241

1446: 3493: 2743: 2361: 2193: 2141: 1932: 1804: 1138: 28: 3056: 2325: 1623: 1519: 3622: 3203: 1565:(20 mi (32 km) from Pacoima Dam) where the exterior walls of the main pre-Field Act building (constructed 1917) were 620:

on the west end. Moving eastward, there is the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, with active

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as an appendix several years later. One hundred seventy-five of the recordings came from these buildings, another 30 were on

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did not provide any strong motion records. Part of the reason there were so many stations to capture the event was a 1965

585:, 300 miles (480 km) to the east. The frontal fault system at the base of the San Gabriel Mountains extends from the 3938: 3542: 3305: 3088: 1603: 1542: 4291: 4174: 3923: 3778: 3293: 3257: 3049: 2670: 2617: 2524: 2450: 2102: 1503: 1229: 1152: 879: 502: 214: 2633: 764:

All segments shared the common elements of thrust faulting with a component of left-lateral slip, a general east–west

4286: 3798: 3567: 3072: 2942: 1878: 1760: 1156: 4119: 3933: 3843: 3768: 3678: 3663: 3507: 3414: 3263: 3221: 3130: 3014: 2654: 1682: 228: 1098:, and the remainder were from ground-based installations near faults, including an array of the units across the 4225: 4084: 3963: 3928: 3888: 3683: 3299: 3275: 3172: 3154: 2880: 1884: 1678: 1622:

Introduced as Senate Bill 520 and signed into law in December 1972, this legislation was originally known as the

1418:. On Interstate 5, the most significant damage was between the Newhall Pass interchange on the north end and the 1346: 1243: 582: 577:

are also part of the anomalous east–west trending Transverse Ranges. The domain of the ranges stretches from the

4164: 4139: 4049: 3988: 3758: 3728: 3597: 2500: 1435: 1235: 665: 768:, and a northward dip, but they were not unified with regard to their connection to the associated underlying 4230: 4169: 4109: 3803: 3738: 3708: 3698: 3658: 3617: 3512: 3378: 3233: 3124: 3118: 1566: 692: 637: 633: 4276: 3983: 3953: 3868: 3823: 3668: 3602: 3592: 3426: 3112: 2935: 2778: 2718: 2700: 2476: 2424: 2401: 2004: 1765: 1408: 578: 4271: 4240: 4159: 4064: 4008: 3958: 3943: 3918: 3898: 3883: 3853: 3838: 3833: 3818: 3788: 3693: 3637: 3632: 3587: 3552: 3444: 3408: 3396: 3384: 3353: 3317: 3311: 3287: 3227: 3215: 3209: 3178: 3166: 3142: 3100: 2964: 2961: 2958: 2638:. from the 9th World Conference on Earthquake Engineering, Tokoyo, Japan, August 2–9, 1988. pp. 1–4. 1898: 1755: 1750: 1597: 1423: 1415: 1197: 1482:

Interstate 210 westbound transition to Interstate 5 southbound overpass collapsed onto San Fernando Road

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faults, with a conservative vertical displacement estimated at 4,000–5,000 feet (1,200–1,500 m).

469: 460: 284: 275: 4266: 4149: 4124: 4029: 3773: 3753: 3718: 3653: 3438: 3402: 3251: 3005: 2094: 1928:

Seismicity of the United States, 1568–1989 (Revised) – U.S. Geological Survey Professional Paper 1527

1653: 1431: 1087: 947: 356: 2996: 1297: 4189: 4134: 4114: 4104: 4099: 4094: 4059: 3998: 3973: 3903: 3848: 3688: 3527: 3522: 3450: 3359: 3323: 3281: 2975: 1459: 1451: 1384: 1110: 1036: 1007: 855: 835: 792: 566: 498: 478: 416: 366: 589:

in the east to offshore Malibu in the west, and is defined primarily by moderate to shallow north-

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during the San Fernando event, a debate began as to whether that low requirement was sufficient.

1562: 1042: 903: 728: 629: 621: 562: 346: 4215: 4179: 4144: 4079: 4034: 3948: 3913: 3893: 3878: 3873: 3828: 3808: 3743: 3723: 3713: 3612: 3572: 3420: 3341: 3239: 3148: 3136: 2990: 1164: 1160: 1079: 1011: 586: 574: 2658: 2601: 1630:. The act restricts construction of buildings designed for human occupancy across potentially 1478: 233: 4220: 4194: 4074: 4069: 3673: 2899: 1731: 1309: 1217: 1147:

The areas that were affected by the strongest shaking were the outlying communities north of

1091: 1074:. This made the earthquake the most documented event, at the time, in terms of strong-motion 979: 617: 456: 220: 2842: 2804: 2559: 2504: 2394:"Ground displacement at San Fernando Valley Juvenile Hall and the Sylmar Converter Station" 2301: 1538: 683: 604: 570: 528: 507: 382: 2290:"The study of earthquake questions related to Veterans Administration hospital facilities" 1970: 459:

in southern California. The unanticipated thrust earthquake had a magnitude of 6.5 on the

8: 2770: 2710: 2692: 2635:

The California Strong Motion Instrumentation Program: Objectives, Status, and Recent Data

2468: 2416: 2393: 1996: 1587: 1534: 1368: 1095: 955: 927: 815: 494: 486: 370: 2846: 2808: 2563: 2508: 2305: 1797:"Preliminary strong motion results from the San Fernando earthquake of February 9, 1971" 2820: 2317: 1575: 1550: 1318: 1046: 1003: 983: 923: 669: 625: 2711:"Strong motion data from the San Fernando, California, earthquake of February 9, 1971" 2693:"Seismological studies of the San Fernando earthquake and their tectonic implications" 2289: 1545:

had 660 schools consisting of 9,200 buildings at the time of the earthquake, with 110

2824: 2613: 2520: 2354:"Damage to constructed works, associated with soil movements and foundation failures" 2321: 2098: 2029: 1903: 1770: 1703: 1466: 1465:

pillars. The spans slipped off of their supports at either end due to lack of proper

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entered into an agreement with the Seismological Field Service (then associated with

1201: 1172: 1168: 1099: 675: 558: 554: 1383:)) were responsible for serious damage to the Sylmar Juvenile Hall facility and the 3462: 2850: 2812: 2760: 2755: 2747: 2731: 2567: 2512: 2378: 2373: 2365: 2309: 2210: 2205: 2197: 2158: 2153: 2145: 1821: 1816: 1808: 1775: 1491: 1427: 1337: 1212: 1187:

Partly detached staircase and severely damaged buildings at the Olive View Hospital

1177: 1059: 548: 1626:, and had the goal of reducing damage and losses due to surface fault ruptures or 2736:"Pattern of faulting and nature of fault movement in the San Fernando earthquake" 2688: 2494: 2067: 2019: 1926: 1352: 1247:

was struck by part of the collapsing building while trying to exit the building.

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buildings that had not been reinforced to meet the new standards. More than 400

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at the southern end of the valley was also identified as having been related to

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The San Gabriel Mountains are a 37.3 mi (60.0 km) long portion of the

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Bouchon, M. (1978). "A dynamic source model for the San Fernando earthquake".

2571: 1656:, building codes only required structures to withstand a lateral force of 0.1 4255: 2735: 2353: 2186:"Seismically triggered landlslides in the area above the San Fernando Valley" 2185: 2133: 2060:

Steinbrugge, K. V.; Schader, E. E.; Bigglestone, H. C.; Weers, C. A. (1971).

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The San Fernando earthquake occurred on February 9, 1971, at 6:00:41 am

600: 524: 325: 312: 3041: 2545:"History of the Alquist-Priolo Earthquake Fault Zoning Act, California, USA" 2496:

California Earthquakes: Science, Risk, and the Politics of Hazard Mitigation

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residences, the highway overpass collapses, and a ceiling collapse at the

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from being overtopped. Schools were affected, as they had been during the

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Sylmar segment, Tujunga segment, Foothills area, and the Veterans fault.

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evidence has shown that the western Transverse Ranges were formed as the

515: 421: 758:

Ground level and overhead view of the scarp at the Foothill Nursing Home

561:, on the south by the Cucamonga Fault, and on the southwest side by the 2447:

Engineering features of the San Fernando earthquake of February 9, 1971

2285: 1617: 1357: 1268: 1264: 1075: 1071: 645: 501:, and other densely populated areas north of central Los Angeles. The 455:) occurred in the early morning of February 9 in the foothills of the 1529: 1205: 975: 951: 1635: 1259: 1254:

Fallen stair towers and damaged basement at the Olive View Hospital

1192: 1126: 1051: 2831: 2751: 2369: 2201: 2149: 2059: 1812: 2674: 2606:

International Handbook of Earthquake & Engineering Seismology

1574:

site. Except for the concrete gymnasium, all of the buildings at

1570: 1546: 1314: 1122: 769: 612: 2414: 1326: 1607:

The Veterans Memorial Community Regional Park in December 2017

1596:, the Field Act was passed the following month, and after the 1742:, a magnitude 6.7 quake which affected many of the same areas 1686:

government building that was shaken to the point of failure.

2131: 2091:

Earthquakes: 2006 Centennial Update – The 1906 Big One

1288:

Collapse of four buildings at the Veterans Hospital complex

1442:

Golden State Freeway – Antelope Valley Freeway Interchange

2769:

Steinbrugge, K. V.; Schader, E. E.; Moran, D. F. (1975),

2066:. Pacific Fire Rating Bureau. p. vii. Archived from 1379:

Differential ground motion and strong shaking (MMI VIII (

703:

Several key attributes of the event were shared with the

532: 493:

The event affected a number of health-care facilities in

2895: 2775: