Back-to-back quakes shake Wichita; strongest one had magnitude of 4.8

Wichita was shaken Wednesday night by back-to-back earthquakes originating in northern Oklahoma.

The U.S. Geological Survey reported that the first quake had a magnitude of 4.3. It was centered 19 miles northwest of Fairview, Okla.

The second was a magnitude-4.8 quake. The epicenter for that one was about 15 miles south-southeast of Alva, Okla.

The USGS reported that the quakes were separated by about 30 seconds.

The first hit at about 10:27 p.m., followed by quake No. 2 at 10:28.

Both quakes were followed within half an hour by lighter aftershocks measuring magnitude-3.4.

The magnitude-4.8 quake is tied for the second-strongest temblor in the southern Kansas/northern Oklahoma region since 2012. The area began experiencing a dramatic increase in seismic activity in 2010 after decades of relative stability.

The strongest quake so far is still the magnitude-4.9 earthquake that occurred near Milan, Kan., on Nov. 12, 2014.

“You’ve had two very good-size events for your area,” Jana Pursley, a geophysicist with the USGS in Golden, Colo., said Wednesday.

She said having two quakes in close succession “happens from time to time.” For example, Peru experienced back-to-back quakes of a magnitude of more than 7 a couple of months ago, she said.

Of Wednesday night’s quakes, she said, “I believe the (first) fault was ready to go and the second one just went along with it.”

Scientists have linked the recent seismic activity in Kansas and Oklahoma to underground disposal of oil-drilling wastewater.

The increase in disposal is a side effect of expanded oil production brought on by a boom in “fracking,” a process that uses high-pressure liquids to break underground rock to reach previously inaccessible pools of oil.

The fracking itself is not believed to be a direct cause of the quakes. The wastewater that comes up with the oil is injected into deep rock formations because it is too polluted with salt and oil to dispose of it on the surface.

This story was originally published January 6, 2016 at 11:20 PM with the headline "Back-to-back quakes shake Wichita; strongest one had magnitude of 4.8."