The 4.0 Ohio earthquake this weekend was a reminder that activities related to hydraulic fracturing, or 'fracking,' can cause seismic faults to shift if not carried out carefully.
The link between "fracking"-related activities and earthquakes was thrown into stark relief over the weekend when a magnitude 4.0 quake struck Youngstown, Ohio – typically not a hot bed of noticeable seismic activity. The quake triggered shaking reportedly felt as as far away as Buffalo, N.Y., and Toronto.
The temblor struck Dec. 31 and was the latest and strongest of 11 minor-to-light quakes that have hit the region since March. The epicenters are clustered around a wastewater injection well for a hydraulic fracturing operation.
Understanding the potential effect hydraulic fracturing or related activities could have on local earthquake risks is one question some researchers hope to answer as they try to develop tools for communities.
Fracking allows energy companies to extract natural gas trapped in shale deposits deep underground. By injecting large quantities of pressurized fluids, drillers can break up the rock, releasing the gas for extraction.
One way to dispose of the waste fluids from the process is to inject them back into porous rock formations deep underground. But if pressurized fluids find their way into faults, the fluids can act like a hydraulic jack, separating locked sections enough to allow them to slip.
The goal of researchers is to provide local or state officials with a means of taking a company's injection plan, plus a knowledge of the rock formation the company plans to use as a dump, and get a rough estimate of the largest quake such a process might trigger.
Seismologist Arthur McGarr says he and his colleagues from the US Geological Survey have worked up such a tool and now are trying to refine it.
The biggest environmental concern around fracking has been groundwater pollution. But Ohio has also had problems with seismic activity. The string of quakes last year prompted the state to ban drilling new wastewater-injection wells within five miles of the well suspected of triggering the temblors. At the state's request, the well itself was shut down Dec. 24.