Though the industry routinely claims that hydraulic fracturing is safe and has been used without incident for decades, the size and scale of the current fracking boom is unlike anything the industry has previously undertaken. As with any industrial process used for the first time on such a massive scale, there have been many unpredicted negative consequences. One such unintended byproduct is earthquakes, which have been caused by the underground disposal of fracking wastewater.
Due to the backlash from nearby residents and local governments over the illegal dumping of contaminated frack fluid, many companies now inject unwanted leftover frack fluid into underground disposal wells. This practice is common in the western shale plays, where the geology is favorable.
In Eastern plays, like the Marcellus Shale, the geology does not allow for underground wastewater injection, so fracking wastewater that is not spread on roads or sent to treatment plants is often trucked out of state (e.g. to Ohio) for disposal in licensed commercial underground injection wells – a process which seismologists believe was responsible for an uncharacteristically large number of earthquakes that occurred in the region in 2011. (The injected water lubricates fault lines, causing them to slip.) Fracking wastewater disposal has also been linked to earthquakes in other states, though oil and gas producers are exempt from federal environmental law designed to prevent industrial waste injection wells from triggering earthquakes.
Though the industry claims otherwise, the link between fracking and earthquakes has been recognized by EPA since at least 1990, when it recognized fracturing and fluid injection as earthquake triggers and recommended extensive seismic monitoring.(Andrew Nikiforouk, “Fracking and Quaking: They're Linked: And scientists, the military, and frackers themselves have known it for years,” The Tyee (B.C.) 11/18/2011