Hydrofracking and earthquakes

Opponents of horizontal hydraulic fracturing for natural gas claim it can contaminate ground water.  Now another possible threat has emerged.  Hydrofracking can cause earthquakes.

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There is no doubt this can happen.  There is even a technical name for it — “induced seismicity.”  The question is how often this occurs and how serious it is.

The Richter scale for measuring earthquake intensity is a logarithmic scale, which means that 5.0 is 10 times as intense as 4.0, 4.0 is to times 3.0 and so on.  The practical meaning of the scale is shown on the chart.  Most of the earthquakes associated with hydrofracking are below 4.0 on the Richter scale.  Still, even a so-called “microquake” can cause damage, and a couple of allegedly induced earthquakes have been above 5.0.

Horizontal hydraulic fracturing consists of drilling a well into deep shale strata, drilling a lateral pipe from the deep well, and using explosives to shatter the shale in which the natural gas is locked.  Then water mixed with chemicals is pumped into the shattered shale to force out the gas or oil.  After the natural gas is forced out, waste water is pumped back into the ground.

The earthquakes result not from the ground settling after the gas is pumped out, as I would have thought, but by the effect of the water-chemical mix on geologic fault lines.  The water-chemical mix reduces friction; it makes the fault lines slippery, and more likely to move.  Defenders of the natural gas drilling industry say that geologic slippage near hydraulic fracturing activity would have occurred with or without drilling activity.

Drilling companies in the United Kingdom have admitted that earthquakes in their area were caused by hydraulic fracturing, and gas drilling in a region of Arkansas has been halted because of concerns about a big increase in the number of earthquakes.  Here in New York, where the Department of Environmental Conservation has put hydrofracking on a fast track for approval, environmental activists claim there have been at least two earthquakes associated with hydrofracking.

This seems to me to be another reason to go slow on hydraulic fracturing until safety and environmental issues can be studied.  The natural gas is not going to go away, or become less valuable, as a result of delay.  And if hydraulic fracturing is allowed to proceed, this is a reason to keep it away from structures such as dams or nuclear power plants, or from major earthquake faults.

Click on Does Gas Fracking Cause Earthquakes? for a comprehensive report on this issue by Joyce Nelson in the Watershed Sentinel, which includes a brief section on earthquake dangers in western New York.

Click on Caudrilla Resources press release for a press release by a drilling company in Britain verifying a link between hydraulic fracturing and minor earthquakes in its area..

Click on A Dot on the Map, Until the Earth Started Shaking for a New York Times report on earthquakes in Arkansas.

Click on Fracking near a nuclear plant in the Barnett shale and Could fracking be at fault for the rare south Texas earthquake? for reports on hydrofracking in Texas.

Click on U.S. Geological Survey report PDF for a U.S. Geological Survey study of a possible connection between hydraulic fracturing and earthquakes in an Oklahoma county.  Click on Fracking May Have Caused 50 Earthquakes in Oklahoma for a comment on that report.

Click on EARTHWORKS – Hydraulic Fracturing and Earthquakes for more links.

Click on Induced seismicity wiki for a Wikipedia article on the subject.

Click on Of Fracking and Frantzen: Is Strong Motion Coming True in Oklahoma? [Added 11/12/11]

Click on A Rock and a Hard Place for an article on hydraulic fracturing in Canada.  [Added 11/12/11]

Click on Fracking sparks earthquake concerns for a good article by Steve Orr in the Rochester (NY) Democrat and Chronicle.  [Added 11/16/11]

Click on Ohio Finds Fracking Waste Injection Well Caused 12 Earthquakes [Added 3/12/12}

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