State oil and gas regulators on Tuesday issued their most far-reaching directive yet in response to a surge in earthquakes, asking operators of nearly 250 injection wells to reduce the amount of wastewater they inject underground by 40 percent. The Oklahoma Corporation Commission wants operators to reduce injections by more than 500,000 barrels of wastewater daily in an area that covers more than 5,200 square miles of northwest Oklahoma. A 5.1-magnitude quake hit the area Saturday: it was the third strongest in state history. The number of earthquakes with a magnitude 3.0 or greater has skyrocketed in Oklahoma, from a few dozen in 2012 to more than 900 last year. Recent peer-reviewed studies suggest injecting high volumes of wastewater could aggravate natural faults.