Event commemorates Northridge quake

Early one morning ten years ago, thousands of Southern Californians sleeping in bed awoke to feel the earth move, buck, and roll. The phenomenon that rocked their world—a powerful earthquake—also shoved structures off their foundations and knocked down sections of freeway overpasses. The temblor was named after the nearby San Fernando Valley community of Northridge, the city closest to the epicenter.

At 4:31 a.m. on January 17, the magnitude 6.7 quake struck about a mile from Northridge and some 18 kilometers beneath the city.

“This was the largest earthquake in an urban area in North America, after the 1933 Long Beach earthquake,” says Margaret Vinci, manager of the earthquake programs office at Caltech. She added that widespread shaking and damage to buildings were reported from Santa Clarita south to Santa Monica. The number of dead totaled 57 people, some struck down by fright-induced heart attacks.

To commemorate the 10-year anniversary of the quake as well as to show off the advances in seismology that were made in the decade that followed, the public is invited to an event titled ‘Learning from the Past, Planning for the Future.’ It will take place on January 17, beginning at 9 a.m., in Beckman Auditorium.

“The focus of the event is what we know today compared with what we knew 10 years ago,” Vinci says. The United States Geological Survey, Caltech, and the Earthquake Country Alliance are sponsoring the day of lectures, movies, displays, and children’s activities, to provide an earthquake primer for those who plan on living in a state prone to quakes.

The list of speakers includes engineers and seismologists from Caltech and the USGS, who will expound on a variety of topics. These include advances in earthquake response systems; scientists’ ability to predict quakes; improvements in detecting and mapping quakes with new technology; and the life-saving quality of rigorous building codes. More information is available online at the event’s website, http://pasadena.wr.usgs.gov/info/nr10/.

The Northridge quake hit along a previously unknown blind thrust fault, later named the Northridge Thrust. It damaged buildings throughout the area, displacing some 20,000 people due to the total or partial collapse of houses, apartment complexes, and office buildings. The estimated economic losses are estimated at between $20 billion and $40 billion.

Although it was a grim milestone in the history of the city, the calamity provided civil engineers, geophysicists, and seismologists with a rich store of facts and knowledge that may help mitigate future such disasters.

One of the technological triumphs is the California Integrated Seismic Network, which covers all of the state. Recently completed, the network of computerized sensors incorporates the TriNet system, which monitors fault activity and ground movement in Southern California.

“We use the seismic network to measure the quakes,” Vinci says. “Within seconds we can determine the magnitude, the time, and the location of the earthquake.” After a temblor of magnitude 3.5 or higher occurs in an urban or densely populated region, the system is capable of producing computerized Shake Maps almost instantaneously. Fire departments and rescue teams use these maps to pinpoint communities that have experienced violent shaking and concentrate their efforts there.

“Shake Maps improve emergency service response time to an earthquake,” Vinci says. “Using the Shake Map, they know where to respond and they can respond faster.”

More than 30 exhibitors will be on hand at the January 17 event to provide demonstrations of the new quake technology, and a kids’ zone exhibit will introduce children to practical tips on how to prepare for a temblor, as well as how to survive the next one.
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