Many commenters wondered if there were hydrofracking operations near the Virginia-based epicenter of the 5.8-magnitude earthquake on Tuesday. The answer is "No," but possible links between natural gas drilling and seismic activity are still being explored.
Currently, there are no hydrofracking wells in the state of Virginia. Hydrofracking sites closest to the quake's epicenter in Mineral, Virgina, can be found in West Virginia; Mineral is 90 miles from the border.
Research has found links between hydrofracking and increased seismic activity. The United States Geological Survey said it's possible for humans to cause earthquakes through such activities. The USGS wrote in its "Earthquakes, Faults, Plate Tectonics, Earth Structure" FAQ that "Earthquakes induced by human activity have been documented in a few locations in the United States, Japan, and Canada. The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies."
In hydraulic fracturing, pressurized water is injected into the ground to crack open rocks containing natural gas. Some of that water is then recovered and disposed of in underground wells — exactly the process described by the USGS.
However, incontrovertible proof of a connection between fracking and quakes remains to be found.
Earlier this year, a slew of earthquakes struck Arkansas, with many occurring near areas of natural gas extraction. Some scientists noted the link, but just as many dismissed it; the Arkansas Geological Survey even said there was "as yet no evidence that the wells used for the salt water are having any effect."
A recent study of seismic activity and hydrofracking in Texas' Barnett Shale produced a similar correlation, but nothing definite. "What we have is a correlation between seismicity, and the time and location of saltwater injection," one researcher involved in the study said. "What we don't have is complete information about the subsurface structure in the area — things like the porosity and permeability of the rock, the fluid path and how that might induce an earthquake."
What we had in Virginia was a rare, large earthquake, the epicenter of which is hours from the nearest fracking site. While studies have found possible links between fracking and quakes, the likelihood that Tuesday's episode was the result of natural gas extraction is highly unlikely.