4.7 Magnitude Earthquake Rattles Parts Of Arkansas, 4029 TV, February 28, 2011:
... Scientists said the earthquakes are not on the infamous New Madrid fault line.
Margaret Guccione teaches Geosciences at the University of Arkansas.
She said the recent swarm of earthquakes could be man made.
"There has been suggestion that rather than a totally naturally phenomena, that this may be exasperated by pumping water down from the wells that they use for fracking of the Fayetteville shale," said Guccione.
Natural Gas Drilling Might be the Cause of Arkansas Earthquakes, Geologists Say, KSPR, February 28, 2011:
The question many have Monday, is why would a 4.7-magnitude earthquake strike outside of the New Madrid Fault System? According to the Arkansas Geological Survey, this is the largest quake outside of the fault system since 1969. ...
Geologists have a guess. "There's a whole bunch of natural gas exploration there. They inject fluids there, and that's been shown to kind of lubricate faults and case small magnitude earthquakes," says Mickus. ...
"There's nothing much tectonically going on here. So, no. That's a good study. It's a good thesis," says Mickus.