Researchers examining quake foreshocks
Researchers are going back and looking at smaller tremors before the magnitude-5.8 earthquake that hit near Pawnee last year in an effort to better understand the links between oil and gas activity and induced seismicity in Oklahoma.
Researchers from the Oklahoma Geological Survey said the information could help put together a model to forecast earthquakes. The presentation was part of a panel on Thursday at the University of Oklahoma Energy Symposium in Oklahoma City.
“We want to be in a position to better forecast larger events,” said Jake Walter, the state’s seismologist. “In the days leading up to that (Pawnee) earthquake, we found very small foreshocks that potentially, if we understand a lot of these sequences, we maybe could forecast that event in the future. Of course, hindsight is 20-20, so we need to test this on other moderate earthquakes.”
The powerful Pawnee earthquake struck Sept. 3, causing items to fall off grocery store shelves and shearing bricks from several downtown businesses. It was followed by dozens of aftershocks up to magnitude 3.6.
Research has linked an increase in wastewater from oil and gas production injected into disposal wells in the deep Arbuckle formation as the main culprit behind the state’s rise in seismicity. Even with better fault data and more injection volume data, it’s still hard to trace it to a specific earthquake event, Walter said.
“When we look at some of the emerging trends in the data and statistical correlation, it’s actually very difficult to tie individual earthquakes or earthquake sequences to individual (disposal) wells,” Walter said. “Oklahoma has been injecting such significant volumes for such a long period of time over a broad area, you have to study the problem in a very holistic sense.”
Michael Teague, Oklahoma’s secretary of energy and environment, said the state has made significant progress in pulling together researchers, regulators and industry since it started the Coordinating Council on Seismic Activity in September 2014. He said the council, which meets monthly, was unfairly criticized at the time for including the energy industry.
“My answer to that was, ‘Who do you think knows best what’s been going on under the state of Oklahoma for the last 100 years?’ It’s the guys who have been hunting around for the oil and gas,” Teague said.
Teague pointed to the speed at which regulators can now take action following earthquakes. When the Oklahoma Corporation Commission issued its first disposal well volume restriction in July 2015, it took about a month to put the plan together. After the Pawnee earthquake in September, a plan was put together in several hours, he said.
“That’s cooperation. That’s coordination,” Teague said. “That’s not anybody doing somebody else’s job, that’s just putting the right people in the mix and saying, ‘We’ve all got to work together to solve this problem.’”