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Geologists Record Widespread Activity On Ste. Genevieve Seismic Zone

In this figure, the dots mark the epicenters of earthquakes of magnitude 2.0 or greater between January 1974 and December 2013. The stars mark the epicenters of earthquakes of magnitude 5.0 or greater since 1800.

Geologists with Indiana University and several other Midwestern schools have identified widespread seismic activity along an “underappreciated” seismic zone in southeast Missouri and southern Illinois. 

The seismic zone is named after a small Missouri town --- but it’s not New Madrid.

The little-known Ste. Genevieve Seismic Zone runs along the Mississippi River from Cairo, Ill. towards St. Louis, Mo. Scientists installed a 140-station seismic network in Missouri, Illinois, Indiana and Kentucky and detected many tiny earthquakes along the Ste. Genevieve Seismic Zone between July 2011 and June 2012. Most ranged in magnitude from 1.3 to 3.0 and were too small to be felt on the surface.

Researcher Michael Hamburger from Indiana University said these instruments can record activity that is too small to be picked up by the regional seismic network.

“The concentration of earthquake activity in this area along the Missouri-Illinois border caught our attention,” Hamburger said.

The Ste. Genevieve system is comparable to the Wabash Valley Seismic Zone along the Illinois-Indiana border. That’s the same system that shook the Midwest in 2008 with the 5.8 magnitude Mount Carmel earthquake.

“I think the potential for larger earthquakes in this area still remains unknown,” Hamburger said. “We certainly know that there is a history of moderate size earthquakes in the range of magnitude 5.0 to 6.0 that have occurred in this area and suggest continuing earthquake hazards.”

The seismic zone has implication because it is in a populated region that includes the cities of St. Louis, Cape Girardeau and Ste. Genevieve.

“The seismic activity that we associate with earthquakes down in the southern Mississippi Valley could perhaps extend to areas further north,” Hamburger said. “There could be additional sources of seismic risk that haven’t been examined in detail yet.”

The study “Seismicity of the Ste. Genevieve Seismic Zone Based on Observations from the EarthScopeOIINK Flexible Array” was published in the November/December 2014 edition of Seismological Research Letters. It is the first published study by the collaborative OIINK geophysical research project. Researchers from Indiana University, Purdue University, the University of Illinois, and the geological surveys in Indiana and Illinois collaborate in OIINK, which stands for “Ozarks, Illinois, Indiana, Kentucky.”

Marine Perot was a KRCU reporter for KRCU in 2014.