Earthquakes have always been a threat in California and other North American regions. But for people in places like Oklahoma, they were unheard of until a few years ago. Scientists have linked this seismic activity to the oil industry and are working on new ways to detect and control what they are calling “man-made” earthquakes.
A Discovery blog headline reads, “Humans Are Creating the Newest Earthquake Zones in North America.” Earthquakes typically occur in areas where there are active fault zones, but in Oklahoma, there’s hasn’t been any major seismic activity until the more recent method of oil and natural gas extraction, called “fracking,” was implemented (1).
Adding to the debate about the cause and effect relationship between earthquakes and fracking, is an announcement by the U.S. Geological Survey last March. As reported by the Los Angeles Times, USGS scientists have determined the threat of damaging earthquakes in Oklahoma is now the same as California because of fracking-related earthquakes.
That statement came after several earthquakes in Oklahoma last year that were big enough to cause damage. The largest was a magnitude 5.8 earthquake that struck near the town of Pawnee. Pawnee is just north of an oil town, called Cushing, which is known as the “Pipeline Crossroads of the World.”
Fracking involves the high-pressure injection of water into shale to break it apart and tap into underground oil and natural gas pockets. It also involves injecting wastewater from the fracking process at a deeper layer. This technique produces tiny earthquakes when the rocks crack open and can produce instability at a deeper level from the wastewater injection.
Scientists say, in the 20 years leading up to the year 2000, there there were only about two earthquakes a year in Oklahoma, with a magnitude of 2.7 or more. They say that number jumped to 2,500 in 2014, and soared to 4,000 in 2015. It dropped back down to the 2,500 level last year, due, in part, to some regulatory efforts.
With 3 million people at risk, Oklahoma regulators are tightening their controls. Kallanish Energy reports, they recently adopted new rules that will force drillers to shut down their operations at least temporarily after a larger quake. The impact on drillers will depend on the severity of the quake (2).
Scientists are also studying recent earthquakes in Northern Texas which have also been linked to hydraulic fracking and horizontal drilling for oil and natural gas. Both of those extraction methods involve the injection of wastewater back into the ground.
The Texas Monthly cited a study published in Science Advances. It reports, before 2008 there were “no reported earthquakes” in the the Dallas-Fort Worth region — but over the last decade, there have been hundreds. The one big geological difference is the way energy is being extracted from the ground (3).
Researchers say they traced the history of fault lines using an ultrasound method, and could track seismic activity as far back as 450-million years. They used the data to create images of rock layers to see when they may have experienced any movement. These researchers say there hadn’t been any seismic activity in that region for 300 million years.
As the Texas Monthly reports, “This isn’t the first study to conclude that the earthquakes in North Texas are man-made, it’s just the most conclusive one.” Another study out of the University of Texas in 2016 also found that energy-exploration activity was connected to earthquakes, and Stanford University published a study last year that used satellite imagery to establish a link.
Texas implemented regulations in 2014 to help control the risk of man-made earthquakes. They require reduced injection amounts and pressure for almost half of newly permitted wells, and, for others, more oversight on injection amounts and pressure.
Texas Railroad Commissioner, Ryan Sitton, said, “Our rules are designed to prevent or minimize any risk, as well as give us the necessary authority to amend permit conditions up to and including shutting a well down as a result of seismicity.”
Stanford geophysicists recently reported that they have come up with a technique that could help reduce the chance of a larger earthquake. It involves the monitoring of very faint tremors that were previously undetected, and using that information to determine when underground conditions are becoming unstable.
As I mentioned, the tiny quakes occur when the rocks crack open from the pressurized injection of water. Co-author, Clara Yoon, said in the report, “You can actually see individual earthquakes occurring next to the section of a well that’s being fracked.”
Researchers say most tremors created by fracking-operations are extremely short-lived. But, when they continue for longer periods of time, even after fracking operations have been halted, this indicates a high level of underground stress and instability. Researchers explain their monitoring technique could provide a crucial red flag before a big earthquake occurs.
Study co-author, William Ellsworth, said in a Phys.org report, “These small earthquakes may act like canaries in a coalmine.” He said, “When they happen, they should be viewed as cautionary indicators of underground conditions that could lead to larger earthquakes.”
As reported by the Phys.org blog, the study could impact the oil and natural gas industry, along with the laws that regulate them. Current rules typically shut down wells after a higher-magnitude quake. With the method developed by Stanford geophysicists, operations could be scaled back before those quakes happen.
Real estate investors who own income properties near oil fracking sites should be aware of the potential impact to their properties. They may even want to consider obtaining earthquake insurance.
(1) Man-Made Earthquakes: Discover
(2) New Fracking Rules: Kallanish Energy
(3) Earthquakes in Texas: Texas Monthly
(4) Stanford Report