Hydraulic fracturing, aka fracking, is coming under more scrutiny because of its possible connection to earthquakes. The fracking earthquake phenomenon is being studied in the U.S., as well as the U.K., where some locations have experienced an uptick in seismic activity that coincides with an increase in nearby fracking operations.
It is known that fracking which involves injecting a cocktail of chemicals and water deep into shale deposits under high pressure to release natural gas, can cause small earthquakes. Larger earthquakes can be caused when high-pressure waste fluid is injected into underground disposal pits, experts say.
We’ve reported on this phenomenon before. In Arkansas, for example, several underground waste disposal sites were closed earlier this year, after communities nearby experienced a surge in seismic activity. In fact, 90 percent of the earthquakes recorded in the state since 2009 have occurred within six kilometers of salt water disposal sites associated with fracking operations.
Last year, Chesapeake Energy and environmental officials in West Virginia were trying to determine if a spike in seismic activity in Braxton County was associated with an injection well located in the town of Frametown. In 2009, the disposal of fracking wastewater was also named a possible suspect in a series of earthquakes that plagued North Texas, in the Dallas-Fort Worth area. Two disposal wells in the area where shut down by Chesapeake “as a precautionary measure” due to the upswing in seismic activity.
Last Monday, a 5.3-magnitude earthquake southwest of Trinidad in southern Colorado sparked more concerns about a possible connection between fracking and seismic activity. According to the Colorado Independent, the earthquake was considered rare but “consistent with the region and historic activity in the area,” so for now, no one is blaming fracking. But a September 2001 swarm of earthquakes in the same area prompted an investigation by the U.S. Geological Survey (USGS) that was unable to rule out fracking activity as a possible cause.
“In recent years, a large volume of excess water that is produced in conjunction with coal-bed methane as production has been returned to the subsurface in fluid disposal wells in the area of the earthquake swarm,” the USGS report reads. “Because of the proximity of these disposal wells to the earthquakes, local residents and officials are concerned that the fluid disposal might have triggered the earthquakes.”
In the U.K., the community of Blackpool, England was rattled by some small earthquakes – the strongest was 2.3 magnitude – in April and May. According to the San Francisco Chronicle, the epicenter of one of the quakes was located less than 500 meters from a well used for hydraulic fracturing. The company fracking the well halted operations and started studying the possible link.
Even last week’s 5.8 earthquake that was centered in Virginia and shook much of the East Coast fueled speculation that fracking activities might be to blame. However, according to the Virginia Department of Mines, Minerals and Energy, no fracking activities are underway near the quake’s epicenter, the Chronicle said.
An expert who spoke to the Chronicle said that smaller tremblors are the most likely to be related to the actual process of fracking.
“You’re not going to get a really big earthquake,” said Mark Zoback, a Stanford University geophysics professor who has studied the issue. “To get a big earthquake, you’d need a really big fault. When these oil fields are being developed, the companies are very aware of where the faults are. They don’t want to do something stupid.”
Injecting waste into fracking disposal pits may cause bigger quakes. As the quantity of water builds up over time, it can change the pressure along a fault line, according to the Chronicle, making any faults more likely to move.
“It’s a little bit like an air hockey table,” Cliff Frohlich, associate director of the Institute for Geophysics at the University of Texas, Austin, and a member of a team that studied the Dallas earthquakes, told the Chronicle. “You pump air into an air hockey table so that when you push something, it will slip.”
