PINCKNEYVILLE, Ill. — The three earthquakes that have hit southern Illinois in the past few months aren't a cause for alarm, according to the region's top earthquake expert.
The three earthquakes include:
- A 2.5 magnitude earthquake happened outside of Pinckneyville on March 5.
- A 3.1 magnitude earthquake happened near Mount Vernon on Dec. 18.
- A 3.6 magnitude earthquake happened close to Standard on Nov. 15.
Even though the earthquakes happened relatively close to each other in both physical proximity and timing, Central and Eastern Region Coordinator of the USGS Earthquake Hazards Program Tom Pratt said that's not exactly out of the ordinary.
"Indeed small earthquakes like these have occurred from time to time in southern Illinois. We thus would not consider them to be 'out of the ordinary'," Pratt said. "Three of them so close in time is a bit unusual, but if earthquakes are distributed randomly in time it is not surprising to get a few closer together than most."
Geologists don't have a good explanation for why the three earthquakes happened in southern Illinois. The area is north of the New Madrid seismic zone where earthquakes have been happening for several thousand years, but Pratt said there is no direct connection between the zone and the recent quakes.
"The chance that these would lead to a larger, damaging earthquake (i.e. are they foreshocks?) is small, but not impossible," Pratt said.
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