Underground injection of frack waste water “almost certainly” caused a wave of earthquakes from Alabama to Colorado, according to a new report issued by the U.S. Geological Survey. The researchers looked at a spike in unusual seismic activity that began in 2001.
A remarkable increase in the rate of M 3 and greater earthquakes is currently in progress in the US midcontinent. The average number of M >= 3 earthquakes/year increased starting in 2001, culminating in a six-fold increase over 20th century levels in 2001. Is this increase natural or manmade?
The report says the use of deep injection wells to dispose of the waste water is the likely source of the increase in seismic activity.
A naturally-occurring rate change of this magnitude is unprecedented outside of volcanic settings or in the absence of a main shock, of which there were neither in this region. While the seismicity rate changes described here are almost certainly manmade, it remains to be determined how they are related to either changes in extraction methodologies or the rate of oil and gas production.
The Environmental Working Group has more on the USGS study.
he USGS authors said they do not know why oil and gas activity might cause an increase in earthquakes but a possible explanation is the increase in the number of wells drilled over the past decade and the increase in fluid used in the hydraulic fracturing of each well. The combination of factors is likely creating far larger amounts of wastewater that companies often inject into underground disposal wells. Scientists have linked these disposal wells to earthquakes since as early as the 1960s. The injections can induce seismicity by changing pressure and adding lubrication along faults.