Geotimes
Web Extra  Friday February 8, 2002

Olympic earthquake watchers

Starting today, millions of people around the world will crowd around their television sets to watch the 2002 Winter Olympic Games in Salt Lake City, Utah. Among the millions is a team of seismologists from the University of Utah, who will be watching the Olympics 24/7 from start to finish. Armed with a new $1.2 million seismic network, they are on the watch for earthquakes and ready to quickly supply public safety information should a quake shake the international event.

With its majestic mountains, the Wasatch Range seems the perfect site for steep competition in Olympic skiing, snowboarding and bobsledding. But beneath the wintry landscape, rocks are slowly grinding, lifting the mountains, and creating the potential for an earthquake. “Here in our Wasatch front urban corridor, the major threat is posed by the Wasatch fault, which is the longest active normal fault in North America,” says Walter Arabasz, director of the University of Utah Seismograph Stations.

And that is where Arabasz and his team of earthquake watchers come into play in the Olympic Games. They have partnered with the U.S. Geological Survey to put a real-time earthquake information system in place in time for the Olympics. “It’s a convergence of needing to have rapid earthquake information available during the Olympic time-frame, but also the building of an Advanced National Seismic System to modernize earthquake monitoring in the United States,” Arabasz says.

Authorized by Congress in 2000, the Advanced National Seismic System (ANSS), calls for installing more than 6,000 seismic sensors to monitor earthquakes in 26 metropolitan areas across the United States. ANSS is only about 5 percent complete now, but Salt Lake City was one of the lucky few cities to get a head start on the project, Arabasz says. “We were fortunate here in our Wasatch front urban corridor to get seed money from this program to be able to accelerate having a basic real-time earthquake information system in place by the time of the Olympics.”

The seismic network features a Shakemap -- a rapidly generated computer map. “I liken it to a Doppler radar image that within five minutes after a disruptive earthquake is able to generate an automated computer map showing the location, severity and extent of actual strong ground shaking”, Arabasz says. The information then goes to the program’s Web site, where anyone, including emergency managers and earthquake scientists can view the results.

A Shakemap relies on a seismograph network of strong motion sensors that continuously record data to upload to the telecommunication system. In Utah, 45 sensors lie within and surrounding the urbanized area.

Seismologists developed the system in southern California after the 1994 Northridge earthquake, and have since routinely produced maps for moderate-sized earthquakes in California and the Pacific northwest, as well as the larger Nisqually earthquake that hit the Seattle area in February 2001.

Olympic venues in Wasatch Front valleys are primarily at risk from moderate earthquakes of magnitude 5 or greater. The probability of a moderate earthquake is about 1 in 1,700 during the 37-day time frame of the Olympics and Paralympics. The risk of a larger earthquake is a little less. “Where there is an active fault such as this near an urban area, the common term is to refer to a large earthquake as a big one -- namely a magnitude-7 event,” Arabasz says. The probability of such an event, he says, is 1 in 3,500.

Even a minor earthquake, however, could endanger alpine venues by triggering landslides or avalanches. The chances of such an earthquake occurring within 9 miles of one of these venues during the Olympics is about 1 in 750.

Arabasz says the Olympic planners did recognize the earthquake risk in this area, but did not give the possibility a sense of urgency. “However, as a seismologist, the last thing I wanted to do was have a disruptive earthquake during the Olympics on my watch,” he says. “Goodness knows any seismologist has a very keen sense of responsibility for public safety, and that’s what we’re about.”

Lisa M. Pinsker

Visit the University of Utah Seismograph Stations Web site  and the ANSS program.


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