UMR researcher: Midwest quakes pack punch

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On February 1, 2005

A New Madrid earthquake packs a more powerful punch than a California quake of the same magnitude, according to a University of Missouri-Rolla researcher.

A New Madrid earthquake packs a more powerful punch than a California quake of the same magnitude, according to a University of Missouri-Rolla researcher.

Dr. J. David Rogers, an associate professor of geological engineering at UMR, says unique geology in the Midwest increases the shaking intensity of even modest earthquakes because seismic energy moves through the dense bedrock underlying the region at very high speeds, then becomes trapped in soft sediments filling river channels and valleys.

That’s one of the messages Rogers will deliver as a keynote speaker Thursday, Feb. 3, at Ameren headquarters in St. Louis during an informational program, "Earthquakes: Mean Business!" The free half-day program, which is part of Earthquake Awareness Week, starts at 8 a.m. and is open to the public.

The New Madrid seismic zone cuts across Missouri, Arkansas, Tennessee, Kentucky and Illinois and threatens additional states in the region.

Instead of focusing on the well-known sequence of magnitude 8.0 New Madrid earthquakes in 1811-1812, Rogers has been researching the 1895 magnitude 6.6 quake, which was centered in Charleston, Mo. According to Rogers, the Midwest is overdue for another earthquake of similar strength.

"This is the earthquake we should be getting ready for," he says. "It’s in our face here and now, not 200 or 300 years from now. This one could happen tomorrow." Rogers and several graduate students have been modeling fictional seismic events of approximately the size of the 1895 quake. As part of their research, they have tried to estimate the impact such a quake would have on long-span bridges across the Missouri River. The preliminary results are sobering, Rogers says. Data indicates ground shaking would be magnified about 600 percent within the flood plain of the Missouri River, a development that would predict soil liquefaction and cause most of Missouri’s existing long-span bridges to collapse. "You don’t need a big earthquake to do significant damage in Missouri," Rogers says.

To lend perspective, Rogers points to the 1985 earthquake that devastated parts of Mexico City and was North America’s deadliest quake in the 20th Century. Although the epicenter was 200 miles away, the areas of Mexico City built on 100 to 150 feet of sediment were destroyed. Most of St. Louis, which is about 125 miles away from the epicenters of past New Madrid quakes, lies on 30 to 100 feet of loose, sandy sediment. In response to the threat of future seismic events, the United States Geological Survey is beginning a five-year program to evaluate the seismic vulnerability of the greater St. Louis area. Fortunately, the last time Missouri had a significant quake, St. Louis didn’t have tall buildings and the rest of the area was mostly unpopulated. The infamous New Madrid earthquakes of 1811 and 1812 rang church bells in Boston, knocked chimneys down in Cincinnati, Ohio, and lifted the Mississippi River 20 feet, causing it to run backward.

California earthquakes don’t impact an area near that large, says Rogers. Rogers champions the creation of a Virtual Geotechnical Database for Missouri and Illinois to house information on surface structures and subsurface features. He proposes to use the database to determine which areas are most vulnerable and who might be at risk in the event of an earthquake.

"They’re doing this in California, Nevada, Oregon and Washington," Rogers says. "But we’ve never had a cooperative effort between states in the Midwest."

Rogers’ concept is supported by the Missouri and Illinois Geological Surveys, both states’ departments of transportation, the St. Louis District of the Corps of Engineers and the East-West Gateway Council of Governments, which oversees development and planning in the St. Louis area.

Those who want to attend the free "Earthquakes: Mean Business!" program in St. Louis should contact Mike Marx of Ameren by Feb. 2 for security reasons: .

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On February 1, 2005. Posted in Research