Fracking Caused Earthquakes, Says British Study
Nick Gilbert
at 10:38 AM Nov 3 2011
Fracking Caused Earthquakes, Says British Study
A CSG derrick in Casino, NSW
Jeremy Buckingham MLC, NSW Greens, Creative Commons
Science // 

Most of the concern in local quarters in relation to coal seam gas mining is usually to do with either the release of the methane gas accidentally into the atmosphere, or the contamination of the water used in fracking, which can potentially then be released into the water table. Well, it turns out we might be able to add one more problem to the list - fracking can aggravate geological faults, causing earthquakes.

A study by a group of geologists, commissioned by the company-under-scrutiny Cuadrilla and based on technical reports from a variety of survey companies , found that the fluids likely caused the pre-existing division between the rocks to lubricate. This allowed the rock formations to slide against each other more easily, causing the 2.3 and 1.5 magnitude quakes.

According to the report, "Most likely, the repeated seismicity was induced by direct injection of fluid into the fault zone. since the pressure spread out over a larger area causing the largest event 10 hours after the injection."

The study also says it is possible, in the worst case scenario, that the fluid already injected could migrate some 600m through a fault, but that the natural formations of the rock mean it is unlikely it would be able to move into further permeable layers.

It also says that the worst estimated magnitude of a further earthquake was level 3.

While the scientists behind the study say there is a low likelihood of further quakes, given the combination of circumstances that led to the initial April tremours, Brian Baptie of the British Geological Survey told New Scientist that there are often faults that go undetected simply because they are to small to be of notice under ordinary circumstances.

"It seems quite possible, given the same injection scheme in the same well, that there could be further earthquakes," he said.

Either way, the fact that CSG mining can cause any kind of unnatural geological movement is somewhat troubling.

[New Scientist]

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