A new study has identified a strong correlation between fracking for shale gas and increased seismic activity in Ohio, USA.
Since records began in 1776, the people of Youngstown, Ohio had never experienced an earthquake, but from January 2011 109 tremors were recorded and new research in Geophysical Research-Solid Earth claims this is highly likely to be due to nearby fracking facilities.
Northstar 1, a well built to pump wastewater produced by fracking in the neighbouring state of Pennsylvania, came online in December 2010 and in the year that followed seismometers in and around Youngstown recorded 109 earthquakes; the strongest being a magnitude 3.9 earthquake on December 31, 2011.
"In recent years, waste fluid generated during the shale gas production – hydraulic fracturing, had been increasing steadily in US. Earthquakes were triggered by these waste fluid injection at a deep well in Youngstown, Ohio during January 2011 to February 2012. We found that the onset of earthquakes and cessation were tied to the activity at the Northstar 1 deep injection well,” said Dr Won-Young Kim.
The study authors found that the onset, cessation, and even temporary dips in activity of the Youngstown earthquakes were all tied to the activity at the Northstar 1 well.
The first earthquake recorded in the city occurred 13 days after pumping began, and the tremors ceased shortly after the Ohio Department of Natural Resources shut down the well in December 2011.
Dips in earthquake activity correlated with Memorial Day, the Fourth of July, Labor Day, and Thanksgiving, as well as other periods when the injection at the well was temporarily stopped.
“The earthquakes were centred in subsurface faults near the injection well. These shocks were likely due to the increase in pressure from the deep waste water injection which caused the existing fault to slip," said Kim.
"Throughout 2011, the earthquakes migrated from east to west down the length of the fault away from the well; indicative of the earthquakes being caused by expanding pressure front."