Northridge Quake Rocks Los Angeles

The Northridge earthquake, which occurred on a previously unrecognized fault beneath California’s San Fernando Valley, demonstrated both the incompleteness of scientists’ mapping of the sites of probable earthquakes and the need for improvements in communities’ preparations for surviving major earthquakes.

Summary of Event

At 4:30:55 a.m. on January 17, 1994, a major earthquake occurred in the vicinity of Los Angeles. The quake measured 6.8 on the Richter scale, and its epicenter was located west-northwest of the city, a mile from the suburb of Northridge. The focus of the earthquake was located about 5 kilometers (a little more than 3 miles) below the Earth’s surface, and, luckily, the rupture followed the fault plane upward, away from the area’s most densely populated neighborhoods. In the 4,000 square kilometers (roughly 1,500 square miles) where the Earth’s crust was severely deformed, the Santa Susana Mountains were reported to have been raised by 40 centimeters (16 inches), to 52 centimeters (20 inches). Although much of its energy was expended in relatively uninhabited areas, the earthquake was felt as far as 400 kilometers (about 250 miles) away, and it affected more than 200,000 square kilometers (more than 77,000 square miles), including the heavily populated areas of Santa Monica, Malibu, Santa Clarita, Simi Valley, and west and central Los Angeles. Disasters;earthquakes
Earthquakes;Los Angeles
Northridge earthquake
Los Angeles;earthquakes
[kw]Northridge Quake Rocks Los Angeles (Jan. 17, 1994)
[kw]Quake Rocks Los Angeles, Northridge (Jan. 17, 1994)
[kw]Los Angeles, Northridge Quake Rocks (Jan. 17, 1994)
Earthquakes;Los Angeles
Northridge earthquake
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[g]North America;Jan. 17, 1994: Northridge Quake Rocks Los Angeles[08800]
[g]United States;Jan. 17, 1994: Northridge Quake Rocks Los Angeles[08800]
[c]Disasters;Jan. 17, 1994: Northridge Quake Rocks Los Angeles[08800]
[c]Earth science;Jan. 17, 1994: Northridge Quake Rocks Los Angeles[08800]

Fortunately, the earthquake struck early in the morning on Martin Luther King, Jr., Day, when traffic was light and few people were at work. Had it occurred on a typical weekday morning, the death toll would certainly have been much higher when office buildings collapsed. Still, 57 people died, and between 80,000 and 125,000 lost their apartments or houses. At the Northridge Meadows apartment complex, where sixteen of the twenty-two deaths caused by building failures occurred, the three-story frame building, which had been constructed in 1972 in compliance with antiquated building codes, collapsed under lateral stress, crushing residents on the first floor. Few single-family dwellings caused casualties, but two houses collapsed downhill and killed three people in Sherman Oaks, and one person died in Malibu when a landslide severely damaged several homes that had been built on steep slopes.

In all, more than 60,000 buildings were damaged; of these, 2,076 were red-tagged, meaning that the owners had one month to complete the repairs necessary to pass reinspection before the buildings could be reoccupied or face demolition by contractors paid by the city. All schools in the Los Angeles Unified School District were forced to close for inspection and repair of damages caused by the earthquake. In the area close to the epicenter, the Northridge campus of California State University and the Northridge Fashion Center shopping mall suffered extensive damage, some of which resulted when automatic sprinkler systems were activated by the shock of the quake. Two major stores at the mall—the Robinsons-May department store and the Levitz furniture store—were damaged beyond repair.

The majority of the damage to office and institutional buildings as a result of the earthquake was caused by the collapse of concrete columns and the warping of steel frames. Eight public parking buildings suffered severe damage or collapse, including the four-level parking garage at California State University, Northridge, which had been built in 1991 in accordance with recent building codes. Many buildings in the area that were made of unreinforced masonry had been rehabilitated after the 1971 San Fernando earthquake through the placement of bolts to secure the walls. Although few of them collapsed, major damage was common in such buildings.

The transportation network in the Los Angeles area also suffered from the inadequacy of earlier building codes. Six major bridges collapsed, and 157 more were seriously damaged, resulting in expenditures for repair and replacement reaching $1.5 billion. The Golden State Freeway (Interstates 5 and 405) and the Antelope Valley Freeway (State Routes 2 and 14) were both severely damaged. Five freeway overpasses fell, and the Gavin Canyon Bridge on Interstate 5 collapsed. This bridge collapse was both dramatic (and hence well televised) and instructive; built in 1967 of nonductile concrete, the structure did not have the flexibility to withstand a sharp seismic jolt.


The Interstate 5 and SR14 freeways collapsed during the Northridge quake.

(National Oceanic and Atmospheric Administration)

Although the Northridge earthquake was costly in lives and property (at an estimated $20 billion in property damage, it was the most expensive quake the United States had experienced up to that time), it had some positive impacts. Providing a real-world test of the building codes, emergency procedures, and public education that were in place, the quake helped to demonstrate what worked, what did not, and where more research was needed.

The Northridge earthquake occurred in an area where another quake had struck in 1971, and some of the structures that had been destroyed in 1971, such as the Olive View Hospital, had been rebuilt with better materials and techniques. Building codes These survived the 1994 quake without much deep structural damage. Other buildings that had only been reinforced with iron rods did not fare so well. Still others, such as the Holiday Inn in Van Nuys, suffered enormous structural damage in 1994 after surviving without much damage in 1971. All of this information contributed to engineers’ knowledge of the requirements for building safety in earthquake-prone areas.

Significantly, although the majority of destruction was found in the vicinity of the earthquake’s epicenter, pockets of intense destruction were found elsewhere, such as in areas of Santa Monica, West Hollywood, and Sherman Oaks. Geologists ultimately tied these localized centers of destruction to the unconsolidated fill, soft mud, and alluvial sediments on which the structures in these areas stood. When saturated with water, these materials liquefy under the effects of an earthquake, depriving the structures built on them of a solid footing.

In the years following the Northridge earthquake, seismologists identified other blind thrust faults like the one responsible for that event, widening the scope of their ability to predict seismic events and prepare for them. Building codes were improved, and programs for teaching earthquake survival skills were implemented. Over the long term, the Northridge event resulted in improvements in scientists’ knowledge of the locations and effects of seismic events that may help to prevent untold loss of lives and property in the future. Disasters;earthquakes
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Northridge earthquake
Los Angeles;earthquakes

Further Reading

  • Bolin, Robert, and Lois Stanford. The Northridge Earthquake: Vulnerability and Disaster. New York: Routledge, 1998. Details the Northridge quake and its aftermath. Includes excellent photographic documents.
  • Coburn, Andrew, and Robin Spence. Earthquake Protection. 2d ed. New York: John Wiley & Sons, 2002. An architect and an engineer provide an integrated account of the effects of earthquakes. Emphasizes the relationships among structural damage, human behavior, socioeconomic factors, and casualty patterns.
  • Hough, Susan Elizabeth. Earthshaking Science: What We Know (and Don’t Know) About Earthquakes. Princeton, N.J.: Princeton University Press, 2002. Good source of basic information about earthquakes. Includes suggestions for further reading and index.
  • _______. Finding Fault in California: An Earthquake Tourist’s Guide. Missoula, Mont.: Mountain Press, 2004. Provides travelers with pertinent information on the locations of earthquake faults. Includes maps, bibliography, and index.
  • Yeats, Robert S. Living with Earthquakes in California: A Survivor’s Guide. Corvallis: Oregon State University Press, 2001. Presents a history of quakes in California and offers suggestions for how to live safely in earthquake-prone areas. Includes bibliography and index.

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