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 officials are investigating whether an injection well for drilling wastes in Youngstown has triggered 11 earthquakes since last March.
But scientists have known for years that injecting drilling wastes underground causes such quakes, says Greenwire, a national environmental-energy news agency.
The U.S. Department of Energy notes on its Web site: "Oil and gas induced seismicity has been dealt with successfully and is well understood," Greenwire reported last week.
A National Academy of Sciences panel has been studying how oil and gas production and other types of energy production including geothermal and carbon sequestration can lead to man-made earthquakes.
The study was requested 18 months ago by U.S. Sen. Jeff Bingaman, D-N.M..
The panel has met seven times since September 2010 and a final report is expected by early summer.
Ohio has 181 injection wells, but problems have only been reported in Youngstown. That includes a 4.0-magnitude earthquake on Dec. 31.
Injection wells in Arkansas have been linked to earthquakes in early 2011. Other states have reported injection well-caused quakes. Oil and gas production has also been linked to earthquakes, Greenwire said.
Nationally, there are 144,000 injection wells in the U..S. that handle drilling wastes under pressure. They handle 2 billion gallons per day of drilling wastes.
The state of Ohio and D&L Energy Inc. on Dec. 30 shut down the Youngstown injection well and began an on-going investigation.
The Youngstown Vindicator reports that D&L Energy has 120 violations at its 32 injection and production wells in Ohio and Pennsylvania in the last 10 years.
The company has not been fined by Ohio, although regulators cited a lack of corrective action in some cases, the newspaper said.