Fracking-Induced Earthquakes in Central U.S.
Two new studies by scientists at the University of Colorado Boulder and the United States Geological Survey (USGS) have found that the recent increase in the amount and magnitude of earthquakes in the Central U.S. is associated with the injection wells used for wastewater from fracking.
Hydraulic fracturing, also known as ‘fracking,’ has been used by petroleum engineers since the 1940s in order to increase well production at oil and gas extraction sites. It is a technique designed to extract oil and gas from shale rock by injecting a mixture of sand, chemicals, and water into the rock at a high pressure; thus widening and opening existing fissures in the shale rock, and allowing for the recovery of oil and gas. This aqueous sand-chemical mixture then ends up as waste by-product once the extraction is completed. Some of it is treated for reuse but the remainder of it is injected into disposal wells located thousands of feet underground. The EPA estimates that there are “144,000 such wells receiving more than 2 billion gallons (7.6 billion liters) of fluid per day.” Injecting so much of this fluid is altering the pressure on the earthquake faults present around these disposal wells – and by “around” – we are talking at least a radius of 10 miles or more surrounding the wells. This is possible because pressure can easily travel underground, so the wastewater itself doesn’t actually need to be disposed directly near a fault to trigger an earthquake.
Up until recently, earthquakes of magnitude 3 or below mainly represented the climbing trend in seismicity, as seen in the Figure above produced by USGS. However in the past 5 years, those earthquakes have risen more and more to a magnitude of 3 or higher – which is the point at which the damage becomes severe. Earthquakes of magnitude 3 or below are sometimes barely even felt; but go above that magnitude, and then there is notable damage to buildings and infrastructure – collapsing of roofs, chimneys, bridges, etc.
The energy companies continue to disagree with such findings – claiming that there is still no proven substantial link between their wastewater disposal methods and seismic activity in the surrounding area. That’s not to say that there isn’t still more investigation to be done – geoscientists are continuing to analyze current injection wells in the Central U.S. to see if they can be linked to any further irregular activity along the faults. But this is an issue that should not be ignored by public and industry alike, for the impacts are only going to get worse by the year.
Photo Credits: http://earthquake.usgs.gov/research/induced/