4 earthquakes in 5 days near Fort St. John, B.C., linked to fracking: seismologist

Multiple minor earthquakes have struck northeastern B.C., in the last five days, according to Earthquakes Canada, each of them likely related to fracking. 

According to the earthquake database, a 4.2 magnitude quake hit northwest of Fort St. John, about 286 kilometres northeast of Prince George, early Sunday morning. That was followed by a weaker 3.2 magnitude earthquake on Monday afternoon. 

On Thursday, two earthquakes struck within less than two hours in close proximity to each other; one had a magnitude of 4.8 and the second was measured as 4.0. 

The Earthquake Canada website lists all four recent quakes as "suspected industry-related" events — in other words, related to fracking in the area, Natural Resources Canada earthquake seismologist John Cassidy said. 

He described them as "induced" earthquakes, related to hydraulic fracturing — also known as fracking — in the area. 

Fracking is a process wherein water, sand and chemicals are blasted at high pressure more than two kilometres underground to release natural gas trapped in rock formations.

"Earthquakes can be induced by a number of, you know, by mining, by oil and gas extraction," Cassidy said. 

"The earthquakes can be induced or triggered by the injection of fluids into the ground or the injection of, in some cases, wastewater."

Cassidy said scientists know these earthquakes were caused by industrial activity because when earthquakes are recorded, the agency checks with the B.C. Energy Regulator to find out what was happening in the area at the time. 

He said the area around Fort St. John is active, but these recent events have been unusual. 

Anyone who felt shaking from the smaller earthquakes would have been within 20 kilometres of the centre of the quake, he said, adding that there were reports of feeling movement as far away as Fort St. John — about 100 kilometres away — for the larger event on Thursday. 

"[It's] pretty common for earthquakes of this magnitude that you would feel shaking," Cassidy said. "It's not causing damage. It's generally mild shaking that would be felt."