Quakes Strike Oklahoma Twice Daily, Compared To Twice Yearly Before 2009

An earthquake with a magnitude of 4.5 that struck near the U.S. crude oil hub of Cushing, Oklahoma on Saturday occurred just days after regulators imposed new rules meant to prevent temblors in the area and said more changes were possible.
The Oklahoma Corporation Commission (OCC), which regulates the state’s oil and gas industry, ordered companies on Sept. 18 to shut or reduce usage of five saltwater disposal wells around the north-central Oklahoma city of Cushing. Saltwater, a normal byproduct of oil and gas work, is put into deep disposal wells that scientists say have contributed to a rash of small and medium-sized earthquakes in Oklahoma since 2009.