The ground in southwestern Indiana is being watched more closely since a June 18 earthquake shook the region.
Monitors installed in Vanderburgh County a few days after the quake have recorded no seismic movements.
The head of the geology department at the University of Southern Indiana, Paul Doss, says the lack of aftershocks is a bit surprising.
The research is meant to explore the seldom-documented Wabash Valley Fault.
Last month's earthquake measured 5.0 in magnitude and caused little damage. However, it was felt at least 250 miles away, including across portions of Kentucky.