Earthquake predictions off, geologist still concerned

A prediction for more frequent and stronger earthquakes in Stillwater hasn’t panned out.

Last year, South African geologist Chris Hartnady released a study that warned Guthrie, Langston and Stillwater areas of earthquakes, called GLS, would experience weekly magnitude 5 earthquakes starting in late 2015.

Hartnady said the fault lines running east and west near the cities make an epicentral alignment, in which several fault lines are close together. The faults he talked about connect to the Nemaha and Wilzetta faults, some of Oklahoma’s largest.

The large amounts of saltwater being pumped into the earth are possibly prompting larger earthquakes, according to Hartnady’s study. Saltwater disposal wells are common in the GLS area.

“If a major part or the whole of the GLS structure is accidentally re-activated in a low-stress-drop regime by wastewater injection, it is capable of generating a significant earthquake in the range Mw5.5-6.5 or greater,” according to the study.

But magnitude 5 earthquakes aren’t the new normal in the GLS.

Soon after Hartnady's study came out, Oklahoma Corporation Commission enacted new rules on wells near earthquake epicenters.

The OCC required wells in Oklahoma and Logan counties to cut back 38 percent of injected wastewater in August 2015. The restriction affected 23 saltwater disposal wells between the counties.

Todd Halihan, Oklahoma State geology professor, said the OCC rules might have affected the prediction, but it is more likely because of the economy.

“With the price of oil being down, a lot of injection has slowed down because of economics,” Halihan said. “So both of those factors have changed the amount of injection from when Chris’s analysis occurred dramatically.” 

Halihan said with the price of oil being so low, it gives scientists more time to find answers and ways to avoid another magnitude 5 tremor.

There were 35 magnitude 3 or higher earthquakes in 2012. Since Feb. 20, there have been 36, according toearthquaketrack.com.

The largest earthquake this year occurred Feb. 13 in Fairview. The magnitude 5.1 quake hit the town and became the fourth-largest earthquake in Oklahoma, according to the USGS.

Fairview has had 40 earthquakes of 1.5 or greater magnitude since March 20, according to earthquaketrack.com.

Halihan said Oklahoma has been lucky so far with earthquake placement. Both magnitude 5 earthquakes have been in remote areas, but he said future quakes might be in more populated places.

“The Earth doesn’t exactly go along with you on your plans,” Halihan said.

Three magnitude 3 quakes were recorded last weekend near Stillwater. The first was March 19 in Perkins, second March 20 in Yale and the last March 20 in Perry.

Hartnady’s study stated the earthquakes work in cycles of accelerated seismic release. Oklahoma’s first cycle started in 2008 and led to the magnitude 5.6 earthquake in 2011 in Prague.

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