Seismic security

Increased regulation may be easing Oklahoma earthquakes

While the earth continues to shudder more frequently than seven years ago beneath Oklahomans feet, the rate of earthquakes in the state in 2016 is down from last year.

The state has been shaken by 448 magnitude-3.0 and greater quakes so far this year, down from the 558 it experienced in the same time frame in 2015, according to data from the U.S. Geological Survey.

Increased regulation on wastewater disposal related to oil and gas extraction could be one reason behind the decline, said Robert Williams, a geophysicist at the United States Geological Survey. Wastewater disposal is linked to quakes in Oklahoma and other states.

Regulators this year increased restrictions limiting wastewater disposal and expanded the area in the state those constraints cover, Williams said. At the same time, a decrease in oil and gas activity led to a smaller volume of water being disposed of, also potentially contributing to fewer quakes, he added.