Oklahoma authorities have set new limits for oil and gas companies after a vast increase in the number of earthquakes, including more than 6,000 last year alone. In 2010, Oklahoma saw just three earthquakes at or above magnitude three, but last year that number rose to more than 900. The quakes have been linked to the injection of oil and gas waste deep underground. On Monday, Oklahoma regulators asked companies in central Oklahoma to reduce the amount of waste they’re injecting by 40 percent. This follows a similar request last month for a northwest region.