Oklahoma is now No. 1 for earthquakes in the United States.
It had 240-plus earthquakes of 3.0 or greater magnitude from January through June.
That total is growing. The state had seven earthquakes last weekend, three of which were greater than 3.0.
Hydraulic fracturing or fracking and injection wells for drilling wastes are the likely causes, the experts say.
Click here to read the latest from the New Republic.
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.