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Local scientists can predict the far-reaching effects of rumblers through the Earthquake Hazard Mapping Project

By Kathleen McLaughlin 

Near its epicenter in southeastern Illinois, the 5.2-magnitude earthquake that emanated from the Wabash Valley fault on April 18 did little but rattle windows. Yet in Louisville, Kentucky, more than 120 miles away, bricks fell from the parapet of a building.

When engineering geologist Robert Bauer heard about the tumbling bricks, he knew why and how it happened. The building sat over an old streambed that was filled with the kind of sandy soil that responds to the slightest tremor. Bauer, who works for the Illinois State Geological Survey in Champaign, says the effect of the recent quake counters the common notion that ground-shaking lessens with the distance from a fault line. Instead, Bauer says, it is the soil that amplifies the energy of a quake: "It's not this perfect bull's-eye."

Scientists can't forecast earthquakes, but they can predict how much the ground will tremble. Bauer and a host of scientists from Missouri and Illinois are gathering data to create maps that will show which parts of the St. Louis area might be most hazardous in an earthquake. The aptly named Earthquake Hazard Mapping Project is sponsored by the U.S. Geological Survey, and it expects to publish the first maps for St. Louis sometime next year.

The St. Louis-area mapping project began in 2004 and is receiving roughly $500,000 from the federal agency, which is overseeing similar projects around the country, says Rob Williams, a geophysicist with the USGS in Golden, Colorado. Though engineers will be the primary users of the maps, Williams says his agency will try and translate the highly technical data into layman's terms.

Being able to calculate and map the intensity of ground-rumbling events, explains Bauer, represents a powerful tool for emergency crews and engineers. Last week, Bauer and Williams presented a progress report on the project to an audience of engineers here. Asked whether the maps will change the way new buildings go up in the future, Williams says, "It's up to your local government officials and your local engineering community."

In any case, the maps could play a key role in updating or revising local building codes, says Greg Hempen, a geophysicist with the St. Louis engineering firm URS Corporation. However, he adds, "It's not up to the engineering community. Developers are more powerful than the engineering community."