TULSA, Okla. (AP) — The number of Oklahoma earthquakes registering a magnitude 3.0 or greater has declined for the third consecutive year after state regulators began directing oil and natural gas producers to close some wells and reduce injection volumes in others.

The number of such quakes began declining in mid-2015 when the state Corporation Commission took action after the quakes were linked to the underground injection of wastewater, according to the Oklahoma Geological Survey.

State seismologist Jake Walter told the Tulsa World he's optimistic the downward trend will continue, but he sa...