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.
Numerous stories were filed this week after federal researchers presented a paper on earthhquakes and fracking-waste injection wells at a national conference in San Diego.
Researchers think increased seismic activity in the central United States including Ohio is tied to wastewater injected below ground by the oil and gas industry, said William Ellsworth of the U.S. Geological Survey.
"Something unusual is going on, and we think many of these earthquakes can be traced to industrial activity," he said.
A total of 13 small earthquakes have struck the Youngstown area in the last 13 months and are believed tied to a now-closed injection well in Mahoning County.
An abstract of the USGS study was published earlier and the full report will be released this summer.
From 1970 to 2000, there were on average 21 earthquakes a year in the U.S. mid-section.
That jumped to 50 in 2009, 87 in 2010 and 134 in 2011, accordinjg to the study.
Earthquakes were also reported in Colorado, Texas, Arkansas, New York, New Mexico and Nebraska and possibly in Oklahoma, Louisiana and Missiissippi.