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| Fracking 'linked to biggest Oklahoma earthquake' | Fracking 'linked to biggest Oklahoma earthquake' |
| (about 2 hours later) | |
| Scientists have linked wastewater injection from hydraulic fracturing to a magnitude-5.7 earthquake that struck the US state of Oklahoma in 2011. | |
| Fracking, as it is known, injects water and chemicals into petroleum wells in a bid to extract trapped natural gas. | Fracking, as it is known, injects water and chemicals into petroleum wells in a bid to extract trapped natural gas. |
| Opponents of the practice say that it risks causing seismic events and contaminating groundwater. | Opponents of the practice say that it risks causing seismic events and contaminating groundwater. |
| The study in Geology shows that "induced seismicity" can occur years after wastewater injection begins. | The study in Geology shows that "induced seismicity" can occur years after wastewater injection begins. |
| Most seismic events linked to fracking have been markedly of smaller magnitudes, and have tended to occur in the first weeks or months of injection. | Most seismic events linked to fracking have been markedly of smaller magnitudes, and have tended to occur in the first weeks or months of injection. |
| By contrast, fracking wastewater was first injected into Oklahoma's Wilzetta oilfields, near the town of Prague, some 18 years prior to the November 2011 series of quakes that included three of magnitude 5 or greater. | By contrast, fracking wastewater was first injected into Oklahoma's Wilzetta oilfields, near the town of Prague, some 18 years prior to the November 2011 series of quakes that included three of magnitude 5 or greater. |
| The new study adds to an increasing body of evidence that the injection of wastewater from fracking - rather than the wellhead injection that extracts gas or oil - is correlated to an increase in seismic events. | The new study adds to an increasing body of evidence that the injection of wastewater from fracking - rather than the wellhead injection that extracts gas or oil - is correlated to an increase in seismic events. |
| A comprehensive review in 2012 by the US' National Academy of Sciences found that "the process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events", but that "injection for disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity". | A comprehensive review in 2012 by the US' National Academy of Sciences found that "the process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events", but that "injection for disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity". |
| However, the report said the number of such documented events over several decades was small compared to the overall number of operations carried out. | However, the report said the number of such documented events over several decades was small compared to the overall number of operations carried out. |
| In April 2012, a study by scientists at the US Geological Survey of the interior of the US found that events of magnitude 3 or greater had "abruptly increased in 2009" from 1.2 per year in the previous 50 years to more than 25 per year - although a number of gas and oil extraction methods may be implicated in the rise. | In April 2012, a study by scientists at the US Geological Survey of the interior of the US found that events of magnitude 3 or greater had "abruptly increased in 2009" from 1.2 per year in the previous 50 years to more than 25 per year - although a number of gas and oil extraction methods may be implicated in the rise. |
| 'Unexpectedly large' | 'Unexpectedly large' |
| But the authors of the new study focus on the significantly larger and delayed events in Prague, which they wrote "necessitate reconsideration of the maximum possible size of injection-induced earthquakes, and of the time scale considered diagnostic of induced seismicity". | But the authors of the new study focus on the significantly larger and delayed events in Prague, which they wrote "necessitate reconsideration of the maximum possible size of injection-induced earthquakes, and of the time scale considered diagnostic of induced seismicity". |
| Study co-author Geoffrey Abers of Columbia University said that "there's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here, " adding that "the risk of humans inducing large earthquakes from even small injection activities is probably higher" than had been believed. | Study co-author Geoffrey Abers of Columbia University said that "there's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here, " adding that "the risk of humans inducing large earthquakes from even small injection activities is probably higher" than had been believed. |
| But seismologist Austin Holland of the Oklahoma Geological Survey said while the study showed a potential link between the earthquake and fracking, "it is still the opinion of those at the Oklahoma Geological Survey that these earthquakes could be naturally occurring". | But seismologist Austin Holland of the Oklahoma Geological Survey said while the study showed a potential link between the earthquake and fracking, "it is still the opinion of those at the Oklahoma Geological Survey that these earthquakes could be naturally occurring". |
| "There remain many open questions, and more scientific investigations are underway on this sequence of earthquakes and many others within the state of Oklahoma," he said. | "There remain many open questions, and more scientific investigations are underway on this sequence of earthquakes and many others within the state of Oklahoma," he said. |
| The topic remains hotly debated in the scientific literature, and between lobbyists and policy-makers, particularly in the UK. | The topic remains hotly debated in the scientific literature, and between lobbyists and policy-makers, particularly in the UK. |
| Links between fracking in Blackpool and tremors in the region led to a government ban on the practice, which was lifted at the end of December 2012. | Links between fracking in Blackpool and tremors in the region led to a government ban on the practice, which was lifted at the end of December 2012. |