http://www.msnbc.msn.com/id/46981365/ns/technology_and_science-science/t/study-ties-oil-gas-production-midwest-quakes/
Odd, this new seismicity map does not quite match the one I posted upthread.
What is the “Midwest” to them? Arkansas and Missouri have small quakes relatively frequently. I notice Pennsylvania has escaped the dreaded 3.0 quake.