MEDFORD, Okla. (AP) -- The U.S. Geological Survey reports small earthquakes in central and north -central Oklahoma that include a magnitude 4.0 temblor six miles northeast of Medford near the Oklahoma-Kansas state line.
The quake was recorded at 4:55 p.m. Saturday. No injuries or damage are reported in the area about 95 miles north of Oklahoma City.
A 2.8 magnitude quake was recorded in the same area and 2.6 and 2.9 magnitude quakes were recorded in the Oklahoma City metro area earlier in the day.
The number of magnitude 3.0 or greater earthquakes has skyrocketed in Oklahoma, from a few dozen in 2012 to more than 900 last year.
Scientists have linked the increase to the underground disposal of wastewater from oil-and-gas production. State regulators are asking oil and gas companies to reduce their wastewater disposal wells.