Understanding the link between fracking and earthquakes in northeastern B.C.

B.C.'s Oil and Gas Commission has suspended fracking operations in an area southeast of Fort St. John until at least 2019 while regulators investigate a series of earthquakes measuring between 3.4 and 4.5 magnitude on Nov. 29.

Though researchers have yet to determine with 100 per cent certainty that the quakes were caused by industrial operations, it is "very likely," according to seismologist Honn Kao of Natural Resources Canada.

In an interview with CBC Daybreak North guest host Audrey McKinnon, Kao explained how researchers determine the cause of earthquakes in the region, and why it is important to monitor the link between oil and gas developments and seismic activity.

The following interview has been edited for length and clarity. Click "Listen" near the top of this page to hear the full conversation, or subscribe in your favourite podcast app.

Have you determined the cause of the earthquake?

As soon as our seismograph network located this event, we were in close contact with the B.C. Oil and Gas Commission to keep them informed of this event's time location and other source parameters.

The B.C. Oil and Gas Commission immediately checked their database to verify if there were any active injecting operations in the vicinity of the reported epicentre. They also contacted the local operators right away.

Based on the reported epicentre, as well as the origin time, B.C. Oil and Gas confirmed with us that there was active hydraulic fracturing nearby at a time when these earthquakes happened.

Based on the correlation in both time and the location, plus that we have determined that this earthquake was a very shallow one, the preliminary conclusion is that that is probably very likely an induced earthquake associated with the hydraulic fracturing nearby.

"Probably very likely" doesn't sound like 100 per cent certainty that is the exact cause. What else needs to be looked at?

We need to do some more serious investigation to determine the physical mechanism that actually links these two phenomena together. And that's exactly what we are doing right now.

Tell me about the connection between earthquakes and fracking. 

The vast majority of fracking operations produce no induced earthquakes at all. But there are quite a number of other examples where hydraulic fracturing can cause felt events, that is, big enough to be felt by local residents.

But not all injection operations have this capacity to trigger events.

Generally speaking, would fracking-induced quakes ever get bigger than this?

This is a very, very important question. The largest hydraulic fracturing-induced earthquake in the world actually occurred in 2015. That is just to the north of this area, the northern Montney area.

That earthquake had a magnitude 4.6. So, Thursday's [Nov. 29's] event was close to the record.

This earthquake had a depth of five kilometres. The average depth of the Montney formation, where this fracking is taking place, is between two and three kilometres. How would fracking be responsible for an earthquake that goes deeper than the fracking itself?

When we inject at a particular location, the injected fluids can change the stress field and that can dissipate into the vicinity regions. So quite often, if it's an induced event, it should be located within a few kilometres of the injection sites. 

Why is it important for us to understand the correlation between fracking and earthquakes?

We know that induced earthquakes are generally very shallow and they can sometimes cause stronger ground shaking at places near the epicentre, even though their magnitudes are relatively small.

Also, because the number of smaller magnitude events increases, that implies that the chance of having relatively larger events increases, as well.

So for these two reasons, the seismic risk associated with the development of shale gas and oil should not be overlooked, and they should be closely monitored as the development of unconventional hydrocarbon resources continues.

With files from CBC Daybreak North