Newspaper article The Christian Science Monitor

Electronic Moles Map Route for Rapid Response When Earth Moves Series: Part 1 Ran on Aug. 11

Newspaper article The Christian Science Monitor

Electronic Moles Map Route for Rapid Response When Earth Moves Series: Part 1 Ran on Aug. 11

Article excerpt

On March 18, 1997, the Mojave Desert pitched and swayed in a magnitude 5.4 earthquake centered underneath the ghost town of Calico, east of Barstow, Calif. Within five minutes, a map appeared on the World Wide Web showing where the temblor hit, how strong it was, and how the shaking varied with distance. It was the first map of a significant quake's ground motions to come from a new network of seismometers sprinkled throughout southern California. Run by the California Institute of Technology in Pasadena, the US Geological Survey, and California's Division of Mines and Geology, TriNet combines the latest in digital quake detectors, computers, and communications to provide nearly immediate feedback on ground motions from quakes. Data from the network, which received its initial funding in January, is expected to help emergency planners respond more quickly to severe quakes, forecast where ground motion is likely to be heaviest, and eventually provide early warning of looming shocks from distant large quakes. As far back as the 1970s, seismologists were intrigued by the prospect of developing a network like this. But "the seismic instrumentation was not that good," says Hiroo Kanamori, director of the Seismology Laboratory at Cal Tech. "Now, it's feasible to build such a system." The TriNet consortium is replacing 300 old seismometers with 200 smaller, more capable digital devices. So far, 50 of the new detectors have been installed, Dr. Kanamori says. For seismologists, the differences between the old and new are striking. For one thing, the new seismometers are able to accurately measure much stronger and weaker motions. As a result, researchers can fill critical gaps in ground-motion information that structural engineers need as they design earthquake-resistant high-rises and other key pieces of southern California's infrastructure. There are two ways to get that kind of information, Kanamori says, "Wait for the next big earthquake, or gather ground-motion information from small and mid-sized earthquakes." By taking the ground's pulse daily, he says, the TriNet array will allow seismologists to estimate the ground motions of a big quake "by adding up the small ones." The network serves up this motion information in two ways, each of interest for different kinds of buildings, according to Thomas Heaton, an engineering seismologist at Cal Tech. For homeowners, the issue is how quickly the ground accelerates during a quake, he says. As the 1994 Northridge, Calif., quake demonstrated, sudden acceleration can yank at the ground underneath a poorly anchored home, leaving several inches of an otherwise intact house hanging over the edge of its foundation. For flexible tall buildings, he says, the ground motion's velocity, which affects the rate of swaying, is critical data for designers. …
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