The number of magnitude 3.0 or greater earthquakes in Oklahoma has declined for the third consecutive year after regulators began directing oil and natural gas producers to close some wells and reduce injection volumes in others.

State seismologist Jake Walter tells the Tulsa World he's optimistic the trend will continue, but says not to expect temblors to end anytime soon.

The Oklahoma Geological Survey says the number of earthquakes began declining in mid-2015, after the quakes were linked to underground wastewater and the state Corporation Commission took regulatory action.

But Walter says quakes will continue for at least a decade "because earthquakes beget earthquakes."

The geological survey says that through late December, 196 quakes of magnitude 3.0 or stronger were detected, down from 302 last year, 623 in 2016 and a record 903 in 2015.

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Information from: Tulsa World, http://www.tulsaworld.com