Geologists Study Potential for New Madrid Quake Impacting Midwest

Sat January 17, 2004 - Midwest Edition

ST. LOUIS (AP) Geologists have begun working with Missouri and Illinois agencies to study St. Louis-area soil and bedrock, looking to better map the danger zones and safer places in case of a serious Midwestern earthquake.

The study announced Dec. 29 comes as many scientists and engineers suspect that the New Madrid Fault beneath the Bootheel area in southeast Missouri could produce a significant temblor within the next half-century or so.

In addition to Missouri, the New Madrid Fault zone includes parts of Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi and Tennessee.

A series of earthquakes was linked to that fault in 1811-12, when the mid-Mississippi Valley was sparsely settled. Lesser-but-damaging quakes followed in 1843 and 1895.

The new study is to take about five years, using records of soil samples from borings taken for public construction projects including highways, bridges and sewers. The study also will examine conditions around Evansville, IN, building on previous studies and projections of relative dangers for southeast Missouri and southern Illinois.

The U.S. Geological Survey already has begun similar work of the Memphis area, slightly closer to the New Madrid Fault than St. Louis.

“Our goal is to provide more specific information on soil conditions within the urban area,” said Jim Palmer, a Missouri Department of Natural Resources geologist. “There’s a lot we can work with.”

Robert Herrmann, a geophysicist at St. Louis University’s Earthquake Center, said the new study will assist in designing earthquake-resistant structures and bolstering old ones to make them safer.

Were the New Madrid Fault to move again with its estimated 8-magnitude force of 1811, “nobody really knows what would happen,” Herrmann said.

“There’d be a good bit of damage, but the city clearly wouldn’t be leveled,” he said.

Existing earthquake maps already assume that sandy soils and river bottom lands are more likely to produce damage during earthquakes than the limestone-and-clay settings for most of St. Louis and its hilly suburbs on both sides of the Mississippi River.

Palmer said the study under way will better be able to accurately pinpoint likely trouble spots.