Survey takes look at quake shaking in three states

ST. LOUIS -- Geologists are launching a study of soils in parts of Illinois, Missouri and Indiana to chart how strongly earthquakes could shake different areas.

The several-year study by the U.S. Geological Survey will not show where earthquakes are expected to originate, only which areas likely would face the worst shaking in a quake.

"We'd love to predict earthquakes, but we can't. But instead we want to predict how often damaging ground shaking will occur," Eugene Schweig, a geologist with the agency, said this week during the Geological Society of America's regional meeting.

The study will combine existing data with new tests planned for St. Louis, across the Mississippi River in neighboring Illinois, and in Evansville, Ind.

The area is affected by the New Madrid Fault, the most active fault in the United States east of the Rocky Mountains. It straddles the Mississippi for more than 100 miles along the southeastern border of Missouri.

Three giant earthquakes in 1811 and 1812 devastated what were sparsely populated areas near New Madrid. Geological Survey scientists estimate there is a one-in-10 chance that a similar quake could happen in the next 50 years. Experts fear a quake of the same size could threaten lives in Memphis, Tenn., St. Louis, and other Midwestern cities.

"There is a 90 percent chance that there won't be an earthquake of that size," Schweig said, though he said moderate earthquakes, more likely, could cause damaging tremors.