Slightly after 8.45 am on Saturday 17 December 2011, the city of Snyder in Scurry County, Texas was shaken by an Earthquake. The quake was small, with a magnitude of 3.2 on the Richter Scale, but extremely shallow, about 5 km bellow the ground according to the United States Geological Survey, and took place about 9 km north of the city.
Location of the 17 December Quake, from the USGS.
Texas does have a small fault zone, which passes through El Paso and Van Horn and causes the occasional minor earthquake, 110 between 1847 and 1994, but this does not pass within 400 km of Snyder, so Earthquakes should be quite rare around the city. Unfortunately Snyder has suffered dozens of Earthquakes in the last four years, which does require an explanation.
Hydraulic Fractionation (Fracking) os a process by which water and chemicals are forced into rocks at high pressure in order to release hydrocarbons, usually natural gas but in Texas the process is also used by oil extractors. The process has been in use in Texas since 2005, and has been credited with creating a major local economic boom (no pun intended), and Texas has always been the US state most friendly to the hydrocarbons industry. Nevertheless people are upset.
Fracking causes earthquakes. This is the point of fracking. Blasting pressurized liquids into subterranean strata is just the same as dynamiting surface deposits, it is intended to fracture the rocks explosively. A fracking operation that did not cause earthquakes would not achieve anything else. Where the industry disagrees with its critics is the scale of earthquakes produced. Fracking operators are typically trying to cause earthquakes with a magnitude of less than 1.0 on the Richter Scale. The Richter Scale is logarithmic, so a magnitude 2.0 quake is 10 times as powerful as a magnitude 1.0 quake, and a magnitude 3.0 quake is 10 times as powerful as a magnitude 2.0 quake and 100 times as powerful as a 1.0 quake. A quake with a magnitude of over 3.0 is thus between a hundred and a thousand times as powerful as a quake of under 1.0, not something that one would expect as an accidental consequence. Despite this fracking operations across the world have been associated with a sharp rise in the number of quakes locally, with quakes in excess of magnitude 3.0 not uncommon. Simply denying responsibility for these quakes is not really an answer; in order to avoid being held responsible the industry will need to provide a plausible alternative explanation for the rise in quake activity.
Earthquakes are not the only problem that the fracking industry has been associated with. Earlier this month the United States Environmental Protection Agency produced a draft report indicating that natural gas extractor Encana was directly responsible for contaminating a drinking water aquifer in Wyoming, something that opponents of fracking have long accused the industry of. The principle behind this concern is quite simple; water for drinking is obtained from aquifers running through subterranean strata; these are sometimes described as 'underground rivers' but this is misleading, the water is running through porous rocks, typically sandstone or chalk, rather than free flowing as in a river. The pressure blasts used in fracking are intended to shatter rocks containing natural gas in order to release the gas, but do not stop at stratigraphic boundaries; they quite happily shatter other rocks too, allowing the chemicals used in the fracking process to permeate into the water bearing rocks, contaminating the water. Again the fracking industry has argued that there is no proof that they are responsible for the contamination, but has failed to provide an alternative explanation.
Simplified diagram illustrating the potential connection between fracking and aquifer contamination.
Texas is extremely drought prone, and Texans are sensitive about water, so many people in Texas have been following events in Wyoming quite closely. The industry in Texas has been quick to point out that the natural gas bearing rocks are deeper beneath the water bearing aquifers in Texas than in Wyoming, but they are also causing larger earthquakes than can be accounted for, so people's concerns will not be dropped easily.
As well as the potential for contaminating aquifers, the fracking industry also uses a great deal of water. The Texas Water Development Board estimated that the industry used 51.1 billion liters of water in 2010. At the same time farms and cities in Texas were suffering extreme water shortages. It is estimated that the water needs of the fracking industry will double by 2020. Potentially brackish water from deep aquifers could be used by the industry, but it is cheeper and easier to use potable water from the shallow aquifers that provide Texas with its water for agriculture and domestic use.