Hydaulic fracturing, or fracking, pumps a water and sand mixture deep below the earth’s surface – past the water table and freshwater aquifiers – into dense shale rock and tight rock formations. In so doing, fracking produces a myriad of long narrow fractures in the rock formation. Advances in technology have allowed the natural gas and oil industry to explore these shale plays, but has had industry critics ask the question: does fracking cause earthquakes?
During hydraulic fracturing, the microseismic events are generally less than magnitude minus two (-2) or minus three (-3) on the Richter scale. (reference 1) A study of hydraulic fracturing-related seismic activity in England found that the combination of geological factors necessary to create a higher-than-normal seismic event was “extremely rare” and such events would be limited “to around magnitude 3 on the Richter scale as a ‘worst-case scenario.” (reference 2)
For reference, a magnitude three earthquake is described by the United States Geological Survey (USGS) as causing “vibrations similar to the passing of a truck.” (reference 3)
An Oklahoma Geological Survey study on seismicity near hydraulic fracturing activities concluded that it was “impossible to say with a high degree of certainty whether or not these earthquakes were triggered by natural means or by the nearby hydraulic-fracturing operation.” The study did note, however, the events under examination were “small earthquakes with only one local resident having reported feeling them. The earthquakes range in magnitude from 1.0 to 2.8.” (reference 4)
- Cardno ENTRIX – Hydraulic Fracturing Study PXP Inglewood Oil Field: http://www.eenews.net/assets/2012/10/11/document_ew_01.pdf.
- “The Geo-mechanical Study of Bowland Shale Seismicity”: http://www.cuadrillaresources.com/news/cuadrilla-news/article/press-release-geomechanical-study/.
- USGS Earthquake web site, 2012: http://earthquake.usgs.gov/learn/topics/mag_vs_int.php.
- Examination of Possibly Induced Seismicity from Hydraulic Fracturing in the Eola Field, Garvin County, Oklahoma: http://www.eenews.net/assets/2011/11/02/document_pm_01.pdf.