There have been more earthquakes strong enough to be felt in Oklahoma this year than in all of 2013, overwhelming state officials who are trying to determine if the temblors are linked to oil and natural gas production. The state on April 6 experienced its 109th earthquake of a magnitude 3 or higher, matching the total for all of 2013, according to Austin Holland, a research seismologist with the Oklahoma Geological Survey. More quakes followed, including a magnitude 4 near Langston about 40 miles (64 kilometers) north of Oklahoma City . A surge in U.S. oil and gas production by fracturing, or fracking, in which drillers use a mix of water and chemicals to coax liquids from rock formations, has generated large volumes of wastewater. As fracking expanded to more fields, reports have become more frequent from Texas to Ohio of earthquakes linked to wells that drillers use to […]