Although the controversial practice of fracking has been directly linked to at least two seismic events small tremors in Garvin County, Oklahoma and Lancashire, England, the wastewater injection that follows fracking is much more likely to set the earth shaking. Thats because injection wells receive far more water than fracking sites, said Katie Keranen, lead author of the Geology study. And unlike at fracking sites, the water is not removed. As pressure builds in these disposal wells, it pushes up against geological faults, sometimes causing them to rupture, setting off an earthquake.
- Oil Addiction, Not Fracking, Caused the 2011 Oklahoma Earthquakes (blogs.scientificamerican.com)