The number of studies that find links between oil and gas extraction and earthquakes is rising. A new report, published in the journal Earth and Planetary Science Letters, adds new evidence by analyzing a series of tremors occurring in areas near the Eagle Ford shale in Texas over a period of three years.
Researchers looked into clusters of seismic events recorded between November 2009 and September 2011, which suggest that the tremors were related to "fluid extraction," Bloomberg reported. Researchers identified 62 small earthquakes, with the vast majority occurring near drilling sites. In one of the counties, 21 of the 22 recorded quakes were within 6.2 miles of wells.
The study also found that since 2010, the average output in the Eagle Ford basin soared from 15,000 barrels a day to 600,000 barrels a day at present. One of the main drivers for this increase has been the use of fracking as a technique for extraction.
Cliff Frohlich, associate director of the Institute for Geophysics at the University of Texas and co-author of the report, explained that pulling out large amounts of hydrocarbons causes underground layers to readjust and fill in the empty spaces created by extraction. This process is felt like a small earthquake. However, he stated that the study found no evidence that injecting fracking fluids to crack the rocks open and release gas and oil actually has any effect on seismic activity.