A strong, 4.3-magnitude earthquake woke many people in the Oklahoma City area early Tuesday and knocked out power to thousands of homes, the latest in a series of temblors that's prompted state regulators to call for more restrictions on oil and gas operators. The quake struck at 5:39am near the city of Edmond, which is a suburb north of Oklahoma City, according to preliminary data from the US Geological Survey. A smaller earthquake with a preliminary magnitude of 3.4 hit the same area about 10 minutes later. No injuries were immediately reported, but the quake knocked out power to about 4,400 homes and businesses; electricity was restored quickly, Edmond spokesman Casey Moore said.
Oklahoma has become one of the most earthquake-prone areas in the world, with the number of quakes magnitude 3.0 skyrocketing from a few dozen in 2012 to more than 720 so far this year. Many of the earthquakes are occurring in swarms in areas where injection wells pump salty wastewater—a byproduct of oil and gas production—deep into the earth. As a result, state regulators have begun reducing the volume or shutting down disposal wells in response. The epicenter of Tuesday's quake was located just outside a previously implemented "cutback zone," where disposal well operators were directed in July to reduce the amount of volume they inject, Oklahoma Corporation Commission spokesman Matt Skinner said. He added that there were no high-volume injection wells operating in the area of Tuesday's earthquakes.