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San Fernando Valley California Earthquakes of 1971 and 1994 |
| This slide set compares two earthquakes that were separated by a distance of 10 miles and a time of 23 years. Disproving the notion that once an earthquake has occurred, an area is safe from future earthquakes, these events affected much of the same area and even some of the same structures. These two events were the largest of 17 moderate-sized main shock/aftershock sequences that have occurred in the Los Angeles area since 1920. The 1971 shock is referred to in the scientific literature as the San Fernando earthquake. The 1994 shock (also in the San Fernando Valley) is called the Northridge earthquake. This slide set compares the two earthquakes. The pictures show the same type of damage in some cases, and effects at the same site in other cases. |
Damage at I-5 and I-210 Freeway Interchange (1971) | |
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1971 The I-5 (Golden State) and I-210 (Foothills) Freeway Exchange. There was damage to both roadway and structures on the completed portion of this freeway, from its intersection with Route 5 to the Maclay Street separation. Throughout this section the freeway appeared to settle on a somewhat uniform grade line. The settling was especially noticeable at the bridges, where it varied from 6 to 24 inches. Pavement was buckled and broken for several hundred feet on each side of the damaged structures. Structural damage varied, from minor damage to wing walls and slope paving, to rotation and settlement of abutments, splaying and cracking of columns, displacement of wing walls, and contortion of the sides of fills. Street sections beneath the various under-crossings suffered damage to curbs, sidewalks, slope paving, and roadway sections. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Damage at I-5 and C-14 Freeway Interchange (1971) | |
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1971 The I-5 (Golden State) and C-14 (Antelope Valley) interchange. Major damage was concentrated at this interchange which was under construction at the time of the earthquake. There was damage to all structures involved, varying from minor cracking and splaying to the loss of complete sections of bridges. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Damage at I-5 and C-14 Interchange (1994) | |
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1994 In 1994, several segments of the I-5 and C-14 interchange north of Northridge collapsed again. These portions of the highway had not been retrofitted. Most of the damage was on the north connector over-crossing and the south overhead section. Photo Credit: Mehmet Celebi, U.S. Geological Survey |
Van Norman Dam partial collapse (1971) | |
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1971 Van Norman Dam (Lower San Fernando Dam). For a length of about 1,800 feet, the embankment (including the parapet wall, dam crest, most of the upstream slope, and a portion of the downstream slope) slid into the reservoir. A loss of about 30 feet of dam height resulted when as much as 800,000 cubic yards of dam embankment was displaced into the reservoir. This material slid when liquefaction of the hydraulic fill on the upstream side of the embankment occurred. The dam was about half full at the time. Eighty-thousand people living downstream of the dam were immediately ordered to evacuate, and steps were taken to lower the water level in the reservoir as rapidly as possible. The Los Angeles Dam was constructed to replace the Van Norman Reservoir. In the 1994 earthquake, some ground movement with minor cracking seems to have occurred at the site. There was significant differential settlement of the ground of about two inches in the northern section, and eight inches in the southwestern section of the site. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Collapsed condenser banks, Sylmar Converter Station (1971) | |
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1971 Collapsed condenser banks at the Sylmar Converter Station. The station was nearly 40% destroyed at a loss of about $22 million. Shown here are collapsed and leaning DC filter capacitor racks. The DC equipment at the Sylmar Converter Station also suffered extensive damage in the 1994 earthquake. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Buckled sidewalks in front of Juvenile Hall (1971) | |
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1971 In front of the Juvenile Hall facility, sidewalks buckled in compression. Fissures opened, measuring 18 to 24 inches wide at the top with a depth of 4 to 5 feet. In the 1994 earthquake, there was minor ground cracking and offsets over limited portions of this site. The cracks totaled about 2 to 4 inches in width in the north-south direction. This site is located about seven miles (11 km) from the 1994 epicenter. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Buckled sidewalks in northern Granada Hills (1994) | |
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1994 "Tented" sidewalks in northern Granada Hills. These are not associated with compressional cracks in the ground, but are the result of pavement decoupling from strong ground shaking. This buckling occurred in an east-west zone of deformation about three miles (five km) long. Major water and gas line breakages occurred in this zone. Much of the deformation in this zone was apparently due to lurching and differential settlement. Photo Credit: Photo Credit: J. Dewey, U.S. Geological Survey |
Damaged home in Crestview Park (1971) | |
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1971 A home in Crestview Park on Almetz Street. More than 700 dwellings were evacuated and declared unsafe after the San Fernando earthquake. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Damaged home north of San Fernando Valley (1994) | |
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1994 Damage to a single family home on a ridge north of the San Fernando Valley. This damage was part of a several block zone in which a number of houses were damaged, surrounded by a larger area that did not experience visible exterior damage. Photo Credit: J. Dewey, U.S. Geological Survey |
Location of fatalities, Northridge Meadows Apts. (1994) | |
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1994 The Northridge Meadows Apartment Building where 16 people were killed. The apartment is located in an area of Northridge of about five square miles where intense damage occurred to this type of apartment. The building had garages on the ends of the first floor and apartments in the middle. Some of these first floor apartments collapsed. Photo Credit: J. Dewey, U.S. Geological Survey |
Aerial view of damage to San Fernando VA Hospital (1971) | |
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1971 Aerial view of the damage to the San Fernando Veterans Administration Hospital and complex. This complex was located in the band of accentuated damage found along the base of the San Gabriel Mountains. The collapsed structure was built in 1926, before earthquake building codes were in effect. Forty-seven of the 58 deaths attributed to the earthquake occurred as a result of the collapse of this structure. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Damage to building at VA Hospital complex (1994) | |
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1994 Damage at Building Three of the Veterans Administration Hospital in Sepulveda. Seismic joints were separated, and pounding of the blocks took place. Structural damage was sufficient to cause temporary evacuation of some buildings in the complex, while non-structural damage by itself was extensive enough to cause closure of several buildings. The non-structural damage was generally greater in upper stories of buildings. This building was also damaged in the 1971 earthquake. Photo Credit: Mehmet Celebi, U.S. Geological Survey |
Damaged Kaiser Permanente Medical Building (1994) | |
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1994 Kaiser Permanente Medical Building, Granada Hills. View from east side. The second story has collapsed. At the right of this picture, the beam that supported the third story rests against the beam that supported the second story, with no intervening space. Photo Credit: J. Dewey, U.S. Geological Survey |
Aerial view of damaged Olive View Hospital (1971) | |
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1971 This building, known as the Medical Treatment and Care Building (in the Olive View Hospital complex) was completed in 1970 at a cost of $25 million. The four towers containing the stairs and day-room areas were built to be structurally separated four inches from the main building. The three towers that failed were supported by concrete columns. When these columns failed, the towers overturned. Note that the base of the tower in this photo has fallen in the basement. After the shock, the building leaned as much as two feet in a northerly direction with nearly all of this drift in the first story. Note also the broken columns on the first floor. The first story nearly collapsed, and the building was ultimately demolished. The structure was located in a band that incurred heavy damage during the 1971 earthquake. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Olive View Hospital replacement fares well in 1994 quake | |
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1994 Shown here is the building which replaced the Olive View Hospital. This new building performed well during the Northridge earthquake, but all of the patients had to be evacuated because of breakage of both sprinkler and chilled water lines. Light fixtures that popped from ceiling grid mounts did not fall because of safety wires. Photo Credit: Mehmet Celebi, U.S. Geological Survey |
Damaged Juvenile Hall Facilities (1971) | |
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1971 The Juvenile Hall Facilities consisted of many one- and two-story buildings constructed of concrete floors, and roofs with concrete frame or reinforced masonry-bearing walls (and in some cases, nonbearing walls). The masonry wall was constructed using "stacked bond." A portion of the two-story administration building collapsed completely into the first story. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Interior damage in San Fernando Mall (1971) | |
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1971 Interior damage to a building in the San Fernando Mall. Severe damage occurred here in 1971, but the area received only slight damage in 1994. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Damage at Bullocks in Northridge Fashion Center (1994) | |
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1994 Northridge Fashion Center's two-story Bullocks Department Store. The second and third floors collapsed onto the bottom story. One column remains standing, and the groove on the column shows where a floor slab would have been attached. Photo Credit: J. Dewey, U.S. Geological Survey |
Damage to parking structure at Northridge Fashion Center (1994) | |
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1994 Parking structure at the Northridge Fashion Center. Two parking structures suffered partial or complete collapse and another was heavily damaged at this shopping mall. In this structure the second level collapsed onto the lower level. Many parking structures performed poorly in this earthquake. Photo Credit: E.V. Leyendecker, U.S. Geological Survey |
Collapsed parking structure, California State University (1994) | |
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1994 Collapsed parking structure at California State University in Northridge. These are reinforced concrete columns. The inside of the structure settled, and the outside fell toward the inside. With each aftershock this structure failed more until finally the west side failed totally. Photo Credit: Mehmet Celebi, U.S. Geological Survey |