New research has confirmed the link between fracking in the oil and gas fields of Western Canada and flurries of earthquakes that have been shaking the region.

The research looked at 12,289 fracking wells and 1,236 waste-water wells in an area along the B.C.-Alberta border. It linked 39 fracking wells and 17 wastewater disposal wells directly to several earthquakes of magnitude 3 or larger. Although only a small percentage of wells caused earthquakes, those earthquakes accounted for more than 90 per cent of the magnitude-3 seismic activity in the region over the past few years.

The link between hydraulic fracturing and earthquakes has been known, but the sweep of the research, published online on Tuesday in the journal Seismological Research Letters, makes the connection clearer and shows the lesser impact of wastewater disposal, long thought to be the major cause of seismic activity.

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The BC Oil and Gas Commission says the research does not raise any safety concerns, but critics disagree.

"I am calling on both the government and the official opposition to join me in supporting a moratorium on horizontal fracking in British Columbia," Andrew Weaver, Leader of the B.C. Green Party, said in a statement Tuesday. "Other jurisdictions, like Quebec, New York, New Brunswick and Nova Scotia, have already suspended the practice and B.C. should follow suit."

In fracking, fluids are injected deep underground to shatter rock and release trapped oil and natural gas. The controversial practice, which has developed rapidly over the past decade, created an energy boom in North America but also raised concerns about groundwater contamination and increased seismic activity. In northeast British Columbia, the number of earthquakes jumped from about 20 a year in 2002 to nearly 200 a year by 2011. Most of the earthquakes are small and might never have been detected except for new arrays of recording devices placed in the region by government, industry and regulatory bodies.

Graham Currie, a spokesman for the B.C. OGC, a provincial agency that regulates the oil and gas industry, said in an e-mail the new research only confirms what was already known.

"The report findings, showing a link between hydraulic fracturing and induced seismicity, have been well understood in British Columbia for the past four years," Mr. Currie wrote, referring to a much smaller 2012 study that found some fracking operations had caused earthquakes in the Horn River Basin.

Mr. Currie said most earthquakes are too small to be felt on the surface, and there are established procedures to ensure public safety.

"Mitigation measures are now in place, including new regulations that shut down industry operations if seismic activity reaches a certain threshold," he said.

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In British Columbia and Alberta, any earthquake of magnitude 4 or higher related to fracking triggers an immediate shutdown of operations until a management plan has been approved by regulators.

Although there has been one fracking-induced earthquake of 4.6 magnitude and one of 4.4 magnitude in British Columbia and two 4.4 magnitude quakes in Alberta in recent years, so far none has caused any damage.

But Ben Parfitt, a resource policy analyst for Canadian Centre for Policy Alternatives, said it may only be a matter of time before a fracking earthquake does serious harm.

"The frightening thing about the linkages between these drilling and fracking activities and earthquakes is that the professionals who look at the industry and try and understand what is going on below the surface actually have no way of predicting what's going to happen," he said.

"People who are trying to understand what this brute-force technology is going to do can't model it. And that is a significant concern," Mr. Parfitt said. "Let's consider where some of this fracking activity is happening. It's taking place in close proximity to some very large earth-filled dams on systems like the Peace River."

Mr. Parfitt said he is worried because thousands of wells are projected to be drilled in the next few years and the operations are growing in magnitude.

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"We know that seismic activity is occurring and that it's getting worse because what's happening with these frack jobs is that they are getting bigger," he said. "There are big, big concerns about what this is going to mean."

Robert Shcherbakov, associate professor at the University of Western Ontario and one of the co-authors of the study, which was done by federal, regulatory agency and university researchers, said it is difficult to assess the risk associated with fracking because only a small number of wells will trigger earthquakes, and it is impossible to predict which ones.

He said most the earthquakes occur in "several well-defined clusters:" the areas around Fox Creek, Rocky Mountain House and Brazeau River in Alberta and near Fort St. John in British Columbia. Those communities are all in the heartland of Western Canada's oil and gas fields.