TULSA, Okla. (AP) — State regulators are asking oil and gas producers in central Oklahoma to restrict wastewater disposal operations to help temper a sharp increase in the number and severity of earthquakes.

Monday’s request from the Oklahoma Corporation Commission covers more than 400 wells across 6,000 square miles.

Commission spokesman Matt Skinner says disposal volumes are about 970,160 barrels a day in the region, and regulators’ goal is 724,000 barrels a day, or about a 25 percent decrease. A barrel equals 42 gallons.

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.

A 5.1-magnitude quake hit northwestern Oklahoma Feb. 13, days before the commission’s earlier directive, which had been in the works since October.