Scientists are delving four kilometres beneath the earth's surface to find out why hydraulic fracturing triggered a 4.5 magnitude earthquake in northeastern B.C in 2018.

The quake was felt in 14 different places, including the construction site of the massive Site C dam, where B.C. Hydro temporarily halted work.

4.5 magnitude earthquake

There were no injuries and no damage, but fracking operations were also temporarily halted.

Soon after, B.C.'s energy regulator determined the quake and several other smaller ones were induced after fracking fluid was injected into a Canadian Natural Resources well site, south of Fort St John.

BC's energy regulator says fracking from one well induced a 4.5 magnitude seismic event in November, 2018, about 22 kilometres from Fort St. John, B.C. (CBC)

Now, preliminary geological research suggests underground rocks in the gas-rich area, between Dawson Creek and Fort St John, are in a "near critical state,"

Researchers say that means just a small increase in fracking fluid pressure may be enough to "critically stress" some ground fractures and faults, a key factor in human-caused earthquakes.

Amy Fox, a geophysicist and owner of Enlightened Science, is leading the research, funded by the B.C. Oil and Gas Commission.

She's been analyzing rocks up to 600 million years old at a depth of four kilometres in a region called the Kiskatinaw.

'Special area'

Fox said some of the underground rocks are highly stressed and even small injections of fracking fluid could induce "seismicity."

"We found some indications that some of the faults underground are what we call ceiling faults, so they're preventing fluid flow between two parts of the rock," she said.

Fox said it also appears that faults in the very deepest "basement" rocks, below where fracking is taking place, have something to do with "induced seismicity," meaning they are more susceptible to earthquakes.

"It's a special area where the regulator wants companies to be very careful ... [about] where they're hydraulically fracturing," said Fox.

'Be very careful'

Fox said the research is using geology to determine risk and to map areas where it's safer to frack.

"Companies aren't just going in there and ... hoping they don't have an earthquake," said Fox, who works primarily with the energy industry. "They're actually assessing the risk and perhaps leaving some areas alone where they think ... something might happen."

Fracking is 'not creating new faults in the earth,' said geophysicist and lead researcher Amy Fox. 'These faults exist ... and we're sort of speeding up a natural earthquake that would have occurred anyway at some point.' (Brennan Linsley/Associated Press)

Most of B.C.'s energy wealth is extracted through hydraulic fracturing.

Energy companies are blasting water, sand and chemicals kilometres underground at high pressure to break rocks and free natural gas.

LNG will boost fracking

And as multi-billion dollar LNG projects proceed, fracking is expected to increase dramatically in northeastern B.C.

And that raises new questions about seismicity.

While earlier research determined that most fracking doesn't trigger earthquakes, 90% of the earthquakes in northeastern B.C. are caused by fracking.

Still, Fox wants people to understand that fracking is not responsible for the fault lines beneath B.C.'s gas fields.

Minimize risk

"These faults [already] exist because of millions of years of geologic history," she said. "We are just speeding up a natural earthquake that would have occurred at some point anyway."

Fox said her ongoing research is using geology to understand and minimize the risks of fracking.

"We need to take a step back and look at all of our information to determine if there are indeed areas that are less risky versus areas that are more risky," she said.

Ben Parfitt is a resource policy analyst with the Canadian Centre for Policy Alternatives.

'Wake up call'

He calls this research "a wake up call."

"It clearly says that earthquakes can be triggered with only "small increases" in the immense amounts of water pumped into the earth during fracking operations," Parfitt said. "It almost certainly means more earthquakes ahead."

Parfitt calls the 4.5 magnitude earthquake that inspired this research the second-largest earthquake in B.C triggered by fracking.

While B.C. continues to study the problem, England indefinitely halted all fracking late last week over earthquake fears. The moratorium came after the country's energy regulator said it wasn't possible to predict the likelihood or size of fracking-induced earthquakes.