After the shaking earth had already demolished many parts of Southern California, a Los Angeles Police officer was unaware of disaster to come while riding his motorcycle to work from his home in Lancaster, north of the quake's epicenter. Unable to see in the dark that a freeway interchange just ahead had collapsed, the officer plunged 30 feet to his death.
At 4:31 a.m., on the crisp morning of January 17, 1994, an unknown fault under Northridge in the suburban San Fernando Valley of Los Angeles, California, ruptured and briefly thrust the earth's crust violently upward.
Greater Los Angeles area residents were shaken out of their beds by the most severe urban temblor since the devastating 1906 San Francisco earthquake.
The initial Northridge quake shook with a staggering Richter magnitude of 6.9, and lasted for more than 20 seconds. The earthquake occurred along a "blind" thrust fault, close to the San Andreas fault. The outcome resulted in one of the most financially destructive natural disasters in American history.
The Northridge quake also claimed 72 lives and inflicted 9,000 injuries, where 1,500 of the injuries were considered severe.
Northridge’s main 6.7 moment magnitude quake broke up many structural foundations, and permanently raised the ground 20 inches in various parts of the San Fernando Valley. Thousands of aftershocks devastated already weathered buildings, trapping many people below the rubble of parking structures and freeway overpasses.
As one of the costliest natural disasters in U.S. history, estimated at more than $40 billion, Northridge can be compared in terms of financial loss to 1992 Hurricane Andrew and the tragedy of Hurricane Katrina.
Occurring 16.5 miles northwest of Los Angeles, the height of the Northridge quake activity was just 11.8 miles below the Earth's crust, making sitting ducks of one of the nation's largest populations. To make matters worse, a "blind" thrust fault quake — a fault that does not extend to the surface — is nearly impossible to predict.
The Northridge earthquake produced the strongest ground motions ever instrumentally recorded in a North American urban setting. Structural damage was recorded as far away as 52 miles from the heart of the shake, and earthquake activity was felt from Las Vegas, Nevada, to San Diego.
Structural damage was reported to more than 12,000 homes, businesses, schools and hospitals, leaving many people homeless for extended periods.
Damage was wide-spread: Sections of major freeways with unwrapped supports and unextended expansion joints collapsed; parking structures and office buildings with concrete framing (non-ductile) collapsed; and numerous apartment buildings suffered irreparable damage.
Damage to wood-frame apartment houses was widespread in the San Fernando Valley and Santa Monica areas, especially to structures with soft first floor or lower-level parking garages. The high accelerations, both vertical and horizontal, lifted structures off their foundations and shifted walls — laterally triggering major fires.
In all, eight Southern California freeways were damaged, including the Highway 14 and Interstate 5 interchange. The interchange's collapse cut off freeway access to Los Angeles for hundreds of thousands of residents of northern Los Angeles County. Ironically, that interchange had collapsed 23 years earlier, during the Sylmar Earthquake of 1971.
On the other side of the Santa Monica Mountains, which separate the valley from the rest of Los Angeles, entire sections of the Santa Monica Freeway collapsed, shutting down a key traffic artery linking Downtown with the city's west side.
The Los Angeles Memorial Coliseum, home to the 1932 and 1984 Olympics, suffered more than $44 million in damage. Farther south of Downtown, the Watts Towers sustained $2 million damage that required seven years to repair. California State University-Northridge was grievously damaged.
In the three years that followed Northridge, more than 681,000 residents applied for assistance from federal and state governments — making the earthquake both a devastating natural and economic disaster.
Although casualties resulting from the Northridge quake were relatively minimal because it was early morning and on the Martin Luther King holiday, will such coincidences save lives next time? The question has been addressed by scientists of the United States Geological Survey (USGS). Following the Northridge earthquake, the USGS has utilized the National Earthquake Hazards Reduction Program (NEHRP) funding to pursue post-earthquake investigations designed to understand the damaging effects of the earthquake.
Since the the NEHRP's induction, the California Department of Conservation has installed seismic hazard mapping and zoning graphs. Some 600 accelerographs, similar to the "black box" recording devices on airplanes, also have been added to further help determine what kind of force buildings, bridges and other structures sustain in a quake.
Although those devices are important in compiling information for building structurally sound architecture, scientists are still not able to predict an earthquake. Researchers at the Southern California Earthquake Center have determined that there is an 80 to 90 percent chance that a temblor of 7.0 or greater magnitude will strike Southern California before 2024.