State’s Biggest Earthquakes—-Not Where Scientists Thought They Would Occur

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The director of the Oklahoma Geological Survey says studies show the biggest earthquakes recorded in the state, including the 5.8 magnitude event last month at Pawnee have been at the edges of vulnerable faults, not close to them where active wastewater injection wells are located.

It’s what Jeremy Boak told a meeting this week of the Society of Exploration Geophysicists in Dallas. More than 5,500 were on hand plus vendors from 250 companies.

The fact those big quakes are at the edges of the zones of highest concern give him pause, according to a report in the Dallas Morning News following Boak’s presentation to a roomful of geoscientists.

As the paper reported, Boak said the pressure created by the injection wells is pushing faults that are relatively far away. Boak said the problem with the state’s earthquakes is what he and other scientists don’t know.

While the quakes affect about 18 percent of the state, their rate of activity has dropped from last June when they reached a peak.

Boak also said studies of the data after the 5.8 magnitude quake showed researchers they had focused in the wrong place and the September event was in a fault they didn’t know existed.