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Scientists monitor Utah mountains for quake during Olympics

SALT LAKE CITY, Utah (CNN) -- As millions of people are watching skiers, snowboarders and bobsledders race down the Wasatch Mountains in Salt Lake City, Utah, this month, scientists will be constantly watching those mountains for signs of earthquakes.

Although the potential for a large quake to shake the 2002 Winter Games is small, if it happens, it could have a devastating effect on the highly populated area.

Emergency officials will get fast information about any sudden Earth movements in the Wasatch fault from University of Utah seismologists who will be manning a new monitoring system of sensors, computers and telecommunications.

University officials said the key feature of the system is the ShakeMap -- a rapidly generated computer map. Within five minutes of an earthquake, the map will give an overview of the location, severity and extent of ground shakes. The data will be similar to the Doppler radar image of a weather disturbance.

EXTRA INFORMATION • Example of a ShakeMap  • Understanding earthquakes  • Utah earthquakes, 2/6/2001 - 2/6/2002

Information from the real-time quake system will be sent to emergency managers so they quickly can direct personnel and equipment to appropriate areas.

The concern comes from the fault under the Wasatch range, which stretches 240 miles (386 kilometers) from central Utah into Idaho, where rock continues to grind slowly, lifting the mountains and producing earthquakes.

Each of the fault's several segments is capable of producing up to a magnitude 7.5 earthquake. There has been a quake of that magnitude about every 300 years during the past 6,000 years, according to the U.S. Geological Survey. The agency said the last big quake was 150 years ago.

Beneath the Salt Lake City area are lake sediments, mostly water-saturated clay, sand or gravel. When an earthquake hits, there is the potential for liquefaction, a phenomenon where those sediments may momentarily lose their ability to support surface structures such as buildings and roads

Experts said a magnitude 7.5 quake could kill up to 7,600 people, injure 44,000 others and cause about $12 billion in damages.

However, the chance of such a "big one" hitting during the time period of the Olympics and Paralympics is a 1-in-3,500, according to Walter Arabasz, director of the University of Utah Seismograph Stations.

It is somewhat more likely for a moderate quake to shake the metropolitan area -- about 1-in-1,700, Arabasz said.

The chances of a minor or moderate quake of a magnitude of 4 or more occurring within nine miles (15 kilometers) of one of the Alpine venues is about 1-in-750, he said. But even those could set off avalanches and landslides.

An earthquake has visited the Winter Games before. A 1998 earthquake in Nagano, Japan, rattled skiers, set off a landslide and shut down trains.

The USGS estimates there are 500,000 quakes around the world every year. Only about one in five of those temblors can be felt and about 100 of the quakes cause damages.

Utah's $1.2 million quake monitoring system was patterned after a $20 million system in Southern California.

Planning began in 1998 and the U.S. Geological Survey (USGS) provided $965,000 in funds and equipment and the state of Utah provided another $235,00 for the system.

Although the Winter Games were a factor, the primary motivation to get the monitoring system in place was to provide long-term earthquake safety for the Salt Lake City area.

Efforts are under way to provide systems for 26 other at-risk U.S. metropolitan areas under the program known as the Advanced National Seismic System (ANSS).

The 1989 earthquake that struck the San Francisco Bay Area, killing more than five dozen people in Northern California, drove home the need for monitoring systems. After that quake, emergency officials had only media reports of damages to guide their response efforts.

Congress in 2000 authorized the ANSS, which is about 5 percent complete. The major progress has been made in the Salt Lake area, the Seattle-Tacoma region and the San Francisco Bay Area.