THE CASE AGAINST HYDROFRACKING - Hydrofracking: What Everyone Needs to Know - page 64

trees and vegetation. In 2005, flowback escaped from a disposal well and contam-
inated an aquifer, the Pecos River Cenozoic Alluvium. Remediation is ongoing; the
company that operated the well had its permit revoked and declared bankruptcy. 73
While such cases are the exception rather than the rule, they undermine public trust
in hydrofracking in general.
Does Hydrofracking Cause Earthquakes?
In addition to concerns over flowback and its potential for contamination of water
sources, earthquakes remain a central focus point for opponents. The two are re-
lated through injection wells.
Hydrofracking has been blamed for causing earthquakes from Arkansas to Eng-
land, though most of these tremors have been so minor as to be nearly undetect-
able. In fact, according to one British report, they “cause no more seismic activity
than jumping off a ladder.” 74 But that's not the entire picture. As the number of
wastewater injection wells has risen since 2001, the number of earthquakes meas-
uring 3.0 or higher on the Richter scale in midcontinent regions that are usually
seismically quiet has surged—from 50 in 2009 to 87 in 2010 and 134 in 2011, rep-
resenting a sixfold increase over last century—according to a US Geological Sur-
vey (USGS) report. 75
Researchers from the Energy Institute at Durham University in England ana-
lyzed 198 reports of induced seismicity (minor quakes that are caused by human
activity) since 1928. They found only three earthquakes they argued were caused
by hydrofracking, all in 2011: one near Blackpool, England, one in the Holt River
Basin in Canada (magnitude 3.8 on the Richter scale), and one in Oklahoma (mag-
nitude 5.7). 76
The Oklahoma quake was caused by the injection of millions of gallons of flow-
back into deep rock formations. The water pressure built up and weakened the
rock; sited near a geologic fault, this apparently set off tremors that hit Prague,
Oklahoma, destroying 14 homes, and damaging almost 200 other buildings. The
tremors were felt across 17 states. 77
Lately, injection wells have been linked to a string of tremors in Arkansas, Ok-
lahoma, Ohio, Texas, and Colorado. According to the USGS, only a fraction of
roughly 40,000 waste-fluid disposal wells have caused earthquakes large enough
to be of concern. 78 While the magnitudes of these quakes is generally small, USGS
reports that their frequency is increasing.