According to the article, “Oil-drilling wastewater pumped into a northeast Ohio well is responsible for 11 minor earthquakes around Youngstown since last spring, including one Saturday, a seismologist tells the Associated Press.”
More minor earthquakes are expected in 2012. The state of Ohio has recommended closing some of these sites.
According to the Christian Science Monitor article, “How fracking caused an Ohio Earthquake”
“One way to dispose of the waste fluids from the process is to inject them back into porous rock formations deep underground. But if pressurized fluids find their way into faults, the fluids can act like a hydraulic jack, separating locked sections enough to allow them to slip.”
The U.S. Geological continues to monitor fracking and groundwater contamination.
This will be an interesting story to follow in 2012, to see if other correlations can be made between earthquake tremors and oil wastewater coming in contact with fault lines.