Area seismicity on decrease but state needs more data

Prof. Todd Halihan describes Oklahoma Corporation Commission’s process and modifications it required for wells within a certain area during an earthquake seminar Thursday in Fairview. (Photo by Emily Summars / Enid News & Eagle)

FAIRVIEW — A seminar Thursday left many unanswered questions re­­garding earthquakes, even though Oklahoma State University Professor Todd Halihan said Oklahoma has more data.

The seminar, “Oklahoma Earth­quakes: Discussing Science to In­­form Policy,” was hosted by the Major County Oklahoma Cooperative Extension Service and Oklahoma State University, in conjunction with the Local Emergency Planning Committee in Fairview.

At the Northwest Technology Center in Fairview, Halihan said the topic of oil and gas in regard to earthquakes can get “messy.”

“There’s two sides: if you look for or produce oil and gas, everyone is going to die and the other version is if you produce or look for oil and gas, it’s a sunshiny day and the economy will flourish,” Halihan said. “When the technical reality is if you do things that are industrial you have slight effects that you have to manage — the risks of hazards, and you need to think about that.”

Last year the Oklahoma Geological Survey announced Oklahoma’s earthquakes were triggered by injection wells, a process of injecting wastewater back into the earth that commonly is used in oil and gas production.

Oklahoma’s seismicity rate has decreased since last year but the issue is not done. He said the decline is bumpy and a decline will not be smooth.

“We look to see the magnitudes are going down and the longer trend of three to six months are (in) decline,” he said. “It shouldn’t go down uniformly but it should have kicks and bumps. It’s an ugly pattern.”

Halihan said Oklahoma will have larger earthquakes, possibly another 5.5 magnitude, before a true decline.

“One thing the state doesn’t want to do is say mission accomplished, we’ve been making these go down and we’ve made it better because in a lot of cases for induced seismicity, some of the largest earthquakes show up when turned down,” he said. “They don’t want to tell people to not worry about it when you’re not in the clear. They’re still watching it but we have seen a decline from the highs we had earlier this year.”

Injection water is commonly placed in a Class II injection well.

Halihan said the water is re-injected into the ground and not used for other things, like irrigation of crops, because of it’s salinity level.

“It is about 150,000 parts per million salt brine,” he said. “The ocean is 35,000. This is incredibly salty stuff.”

The cost to desalinate the water can outweigh oil exploration costs, Halihan said.

“In running an injection well — turning it off and on hurts more than being continual with it,” Halihan said, in how it impacts seismicity. “We didn’t care too much as long as the waste was properly disposed of so the state would get reports from companies several months later. It wasn’t harming anything so it would come in on a piece of paper and someone would log it.”

Halihan said when concerns changed from preserving fresh water on top to seismicity and pressure changes, Oklahoma’s data began to change.

“It changed in how we’re managing it,” he said. “California would say, ‘you’ve had a four (magnitude earthquake). We have those all the time.’ But, our fours are interesting. Our fours are not their (California’s) fours so you (scientists) get a ‘did you feel it’ response.”

The United States Geological Survey has a survey anyone can fill out after an earthquake, including how it felt and location.

California had 804 people respond to an earthquake, stating they felt light shaking. It was a 4.8 magnitude quake. In Oklahoma, a 4.8 magnitude received a strong shaking statement from 2,700 respondents. In California, the earthquake pattern was circular. In Oklahoma, it was elongated along the fault.

“We don’t have great data about the state’s basement and what it looks like because no on ever made money on it,” he said. “There’s things we could spend money on that would be quite useful that we may not have done since the 1950s.”

Halihan said Oklahoma doesn’t have a lot of data on fault locations, basement tectonics, fluid pressures and stress fields.

Ultimately, the topic needs more funding, he said. To be effective, he said research funding should be at about $50 million.

“You’d have to spend money to do some real science,” he said. 

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