Man-made Oklahoma earthquakes are increasing in frequency, transforming it from an area of little activity to a hotspot for quakes in less than a decade.
While earthquakes are sometimes an unavoidable part of living certain places on Earth, activity from humans has the potential to create earthquakes as well. Such is the case with the Oklahoma earthquakes that have been attributed to activity by the oil and gas industry.
The Conversation reports that there was only one earthquake of magnitude 3 or greater in 2008, but by 2015 there were an astounding 903. A magnitude 3 earthquake is big enough to be felt by humans, and while not all of the quakes were severe enough to cause damage, activity from the oil and gas industry injecting their byproduct of saltwater into the ground has continued to cause issues in an area that was previously considered seismically normal.
A study published in the journal Science found that the size of the man-made Oklahoma earthquakes is strongly tied to the depth of the wells in which the saltwater is injected. Reducing the depth of the wells from the oil and gas industry could significantly reduce the occurrence of the earthquakes moving forward.
The Conversation reports that since 2011, well operators have injected around 2.3 billion barrels of fluid each year into layers of sedimentary rock deep underground. By injecting that much wastewater, there has been an unprecedented effect on the severity of the Oklahoma earthquakes.
Although this most recent study published in Science is the latest to establish between the Oklahoma earthquakes and the depth of wastewater injection, the link between the two occurrences was established back in 2013 in a paper that shows another strong association between the injection zone and earthquakes.
Recent regulations introduced in 2015 have somewhat reduced the number of earthquakes, but the actual drop in seismic activity hasn’t been nearly as high as initially expected. A number of powerful Oklahoma earthquakes continued to strike, with the largest in state history hitting in 2016 – a good while after the regulations were put into effect. The Conversation also suggests that the reduction in earthquakes is simply due to a reduction in mining due to lower oil prices.
The study published by Thomas Gernon, Associate Professor in Earth Science at the University of Southampton, U.K., and his colleagues, “used computer models of the relationship between seismic activity, geology, and injection operations using six years’ worth of fluid disposal data from across the state. It shows that the more saltwater is injected and the greater the depth it goes to, the larger the resulting earthquake.”
Gernon states that “Raising injection well depths further above the basement rocks in key areas could significantly reduce the annual energy released by earthquakes, in turn making larger earthquakes less likely. Current regulations can require operators to either reduce injection or raise the depth at which wells inject relative to the crystalline basement, but often the amount is not given or not based on scientific evidence.”
“We hope our approach could help regulators test the effects of new regulations and the potential impact of new injection wells.”