The B.C. Oil and Gas Commission has shut down oilfield fracking operations for at least 30 days in northeastern British Columbia while it investigates earthquakes that occurred there on Nov. 29.

The regulator says the seismic events, which measured between 3.4 and 4.5 magnitude, took place near hydraulic fracturing operations being conducted about 20 kilometres southeast of Fort St. John by Calgary-based Canadian Natural Resources Ltd. The practice is also known as fracking.

It says the company immediately suspended work on Nov. 29 and it won't be allowed to resume without the written consent of the commission. Six companies in or close to the area have also suspended fracking operations.

The area closed off is 11.6 kilometres by 6.4 kilometres in size, says the regulator.

According to Natural Resources Canada, the 4.5 magnitude earthquake was felt in Fort St. John, Taylor, Chetwynd and Dawson Creek but did no damage. It was followed by two smaller aftershocks.

Fracking involves injecting large amounts of water, sand and chemicals into a well to break up tight rock underground and allow trapped oil and gas to flow.

The technology, along with injecting oilfield liquids into disposal wells, have been linked by the B.C. commission to previous incidents of "induced seismicity," although it notes on its website none of the events in B.C. have resulted in hazards to safety or the environment or property damage.

Earthquakes usually small, shallow

Honn Kao, a seismologist with Natural Resources Canada, told CBC's Daybreak North that most fracking operations don't produce induced earthquakes, and when they do, they're relatively small and shallow.

The earthquake last week came close to matching the world's largest fracking-induced earthquake which occurred a little further north in 2015 and registered magnitude 4.6.

The Fort St. John and District Chamber of Commerce says the shutdown is an attack on the already suffering oil and gas industry.

"We've gone through three bad years," said Ramona McDonald, the chamber's president.

"We do not need to go through another three years or another month even of shutdowns, because people are finally just starting to get back to work."

Shutdown hurting business owners

McDonald, who runs a business that serves the oil and gas industry, says the shutdown could cost her upwards of $100,000 in lost contracts.

She says the shutdown is unnecessary and that there's already scientific evidence backing the link between fracking and earthquakes.

"This has been studied for a number of years ... and has been going around and around in circles," she said.

Gas drilling in northeastern B.C. is expected to ramp up dramatically once the Pacific Northwest LNG project proceeds.

Natural Resources Canada says there's still not complete certainty the earthquake was caused by fracking, although the two events seem strongly correlated.

"We need to do some more serious investigation to determine the physical mechanism that actually links these two phenomena together," said Kao, the seismologist.

Injecting oilfield liquids can change the stress field in a location and dissipate in the vicinity, which is what investigators are looking at right now, Kao said.

And although the earthquakes have so far been small, they suggest a greater risk of larger seismic activity, he said.

"The seismic risk associated with the development of shale gas and oil should not be overlooked."