Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
Ohio says its new rules for brine monitoring and disposal will be among the toughest in the United States.
The new rules are resulting from an investigation by the Ohio Department of Natural Resources on a link between a Mahoning County injection well and a dozen earthquakes near Youngstown in the last year.
The state on Friday released a 24-page preliminary report that concludes that the earthquakes were triggered by injecting briny wastes from Pennsylvania's Marcellus shale into the D&L Energy injection well in Youngstown Township.
The quakes stemmed from "a number of coincidental circumstances" including unknown geologic fault lines under the 9,000-foot-deep injection well, ODNR said.
"our evidence strongly suggests that the injection fluid lubricated a previously unmapped fault and contributed to seismic activity," said ODNR spokesman Carlo LoParo. "It was an unfortunate situation and the operator drilled the well to specifications and operated within all permitted levels,"
The state agency outlined a number of steps to tighten regulations on injection wells.
Ohio currently has 176 operating injection wells.
Click here to access the state's report.