IU geologists identify new seismic zone near Illinois-Missouri border
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BLOOMINGTON, Ind. -- Geologists at Indiana University have characterized widespread seismic activity in an area they call the Ste. Genevieve Seismic Zone, suggesting a greater possibility of earthquake effects than was previously recognized in southwestern Illinois and eastern Missouri.
The study, in the November/December 2014 issue of Seismological Research Letters, is the first published research to result from the collaborative OIINK geophysical research project, a collaborative effort among Indiana University, Purdue University, the University of Illinois and the Illinois and Indiana state geological surveys.
At the heart of the project is a 140-station seismic network, a system of detectors installed as part of the National Science Foundation-funded EarthScope USArray project. The acronym OIINK refers to the areas in which the detectors were installed: the Ozarks, Illinois, Indiana and Kentucky.
Michael Hamburger, professor of geological sciences at IU Bloomington and a co-author of the study, said characterizing seismic activity in the zone could be important because of its location.
“It’s an underappreciated zone of seismic activity that has potential implications for St. Louis and other populated areas in eastern Missouri and Southwestern Illinois,” he said. “It’s comparable to the Wabash Valley Seismic Zone in western Indiana, which is capable of producing moderate-sized earthquakes every few decades and perhaps has the potential for larger earthquakes.”
Xiaotao Yang, an IU doctoral student in the Department of Geological Sciences, is the lead author of the paper. Co-authors also include IU geologist Gary Pavlis, principal investigator for the OIINK project; Elizabeth Sherrill, who worked on the study as an IU undergraduate; and John Rupp, senior research scientist with the Indiana Geological Survey. Other co-authors are Hersh Gilbert of Purdue University; Stephen Marshak of the University of Illinois; and Timothy Larson of the Illinois State Geological Survey.
In addition to being near populated areas, the Ste. Genevieve Seismic Zone is an area of geological interest. It partially underlies the Ste. Genevieve fault zone, near the divide between the billion-year-old Ozark Dome and the younger sedimentary rock of the Illinois Basin. One objective of the OIINK project is to study relationships between faults at the Earth’s surface and seismic activity deep underground.
“We don’t really have a clear picture of the relationship between the deeper seismic activity and the fault systems nearer the surface,” Hamburger said. “A key question for geologists is whether these are active faults. And these findings hint that the Ste. Genevieve fault itself, or perhaps underlying or related fault systems, are potentially seismically active.”
The four-year, $1.3 million OIINK project involves the deployment of 140 state-of-the-art seismographs across a broad swath of the Midwest, from Missouri through southern Illinois and Indiana, through western and central Kentucky. The current study is based on results from the first phase of the project, which collected data in the Missouri-Illinois border area from July 2011 to June 2012.
Thanks to the density and sensitivity of the detectors, researchers were able to record numerous small earthquakes -- with a magnitude as low as 1.3, too weak to be felt at the surface -- and to distinguish the quakes from quarry and coal mine blasts that also produce seismograph readings in the region.
While the central U.S. isn’t usually thought of as being at high risk from earthquakes, it includes areas of seismic activity, such as the region along the New Madrid fault system, which runs from southwestern Illinois through Missouri and into Arkansas. The system was responsible for a series of powerful earthquakes in 1811 and 1812 that destroyed the town of New Madrid, Mo., caused waves that swamped boats on the Mississippi River and produced shaking hundreds of miles away.
The region remains seismically active, with the 2008 Mount Carmel Earthquake, centered in southeastern Illinois and southwestern Indiana, causing damage from St. Louis to Louisville, Ky.
Hamburger said results from the current study and future research from the project will become part of the scientific basis for revised earthquake hazard assessments when the U.S. Geological Survey next updates its national seismic hazard maps. Reporters may contact Steve Hinnefeld at 812-856-3488 or email@example.com for a copy of the paper.