An earthquake that rumbled the region in Banff National Park has been downgraded to a 3.7 magnitude.
Canadian earthquake scientists say the earthquake’s epicentre was near Grouse Peak in the northeastern corner of Banff National Park, about 33 kilometres east of Lake Louise, 55 km north of the Banff townsite and 70 km north of Canmore.
Andrew Schaeffer, an earthquake seismologist with Natural Resources Canada, working for the Pacific Division of the Geological Survey of Canada, said the earthquake that struck at 4:39 a.m. on Sunday (Jan. 26) was felt lightly in Banff, Lake Louise and Canmore.
“Every once in a while an earthquake like this gets released so it’s a completely expected phenomenon for the Rocky Mountains,” he said.
“We just don’t see them particularly frequently and we don’t see them very large very often either.”
Earthquake magnitudes are all reported on a magnitude scale, which is commonly referred to as the Richter scale.
Schaeffer said analysts and researchers at the Geological Survey of Canada and Natural Resources Canada looked into Sunday morning’s earthquake in much more detail on Monday (Jan. 27) to come up with a more accurate picture.
“We’ve determined a new magnitude for it, which is a more precise measure of the energy released, and our current magnitude for this is 3.7 MW, which we refer to as a moment magnitude,” he said.
“In all honesty, the reduced size of the earthquake as a 3.7 matches what we observed much better.”
In the end, Schaeffer said there were only about 15 people who reported feeling the earthquake.
“If this had been a real 4.5, we would have expected to have gotten a lot more ‘felt’ reports from Lake Louise, from Banff, from Canmore,” he said.
“Having the most accurate magnitude as a 3.7 fits quite well with the observations of how far and how widespread it was felt, which wasn't that widespread.”
The initial Canadian report was a 4.5 ML magnitude, which is a local magnitude, while the United States Geographical Survey reported a 4.2 MB, which stands for body wave magnitude.
Schaeffer said just because the numbers don’t match up doesn’t mean they are incorrect; rather a slightly different part of the wave is measured to come up with an estimate.
“It gets a little complicated with all these magnitudes and the things that are reported right at the beginning are often preliminary,” he said.
“We’re trying to get a quick assessment to establish how big it was and then over the coming days we take a look in more detail and come up with a more precise estimate.”
The earthquake was also initially reported by the Geographical Survey of Canada at 14 km deep, but it is now estimated to have been five kilometres below the earth’s surface.
“The more precise solution looking at the wiggles, so to speak, in much more detail, we estimate that it’s quite a bit shallower,” Schaeffer said.
While the Town of Banff did not receive any reports from the community, several local residents wrote on social media that they felt it. “Thought it was a derailment,” said one resident on the local Facebook site Overheard in Banff.
On Feb. 13, 2021, Banff experienced an earthquake measuring a magnitude of 3.9 about six km north of the Banff townsite, which rocked homes and buildings throughout Banff and Canmore and beyond. It was recorded at a depth of 17.3 km.
Following a loud boom and buildings starting to shake when that earthquake struck near Lake Minnewanka at 6:33 p.m., emergency crews in Banff and Canmore were quick to investigate and check for any damage.
In neighbouring Canmore, Canmore Fire-Rescue had vehicles out investigating and ready to assist. In the end, there were no reports of damage.
TransAlta operating crews were dispatched to complete visual inspections of all dams, including Lake Minnewanka, and power generation facilities and associated infrastructure west of Cochrane.
On Oct. 17, 2014, an earthquake registering a 2.7 magnitude was felt by Banff residents at 5:42 p.m. Its epicentre was about four kilometres southwest of the Banff townsite.
While Alberta’s seismic activity remains low in the Rocky Mountains, Schaeffer said earthquakes do happen from time to time.
“There’s a few historical earthquakes going back some hundreds of years ago of magnitude sixes or so in the western Rocky Mountains,” Schaeffer said.
“There is not a big concern for these earthquakes in the Rocky Mountains, but they are a surprise every once in a while.”
Since 1985, Schaeffer said there have been six earthquakes in the magnitude 4.0 range and 68 registering in a magnitude 3.0 range within a 200 km radius of the earthquake that occurred in Banff on Jan. 26.
He said many are located further north outside the park and are suspected to be related to oil and gas activity.
“There’s actually very few earthquakes of magnitude 3.0 and higher within the Rocky Mountains themselves, but they’re not unexpected,” he said.
Schaeffer said the reason for fewer earthquakes here is because the Rocky Mountains are a very old mountain belt.
“They were being formed through compression and the building of British Columbia tens to hundreds of millions of years ago, and that puts a lot of stress into the crust of the earth, and so early on, hundreds of millions of years ago, there would have been lots of earthquakes,” he said.
Schaeffer said over time the Rocky Mountains have not been an area of active deformation, which refers to the changing earth’s surface caused by tectonic forces that are accumulated in the crust and then cause earthquakes.
“This is now off the coast of Vancouver Island and Washington and now the Rocky Mountains don’t have earthquakes all the time,” he said.
“When they do, ones like on Sunday morning, that is a release of stress that’s been built up for many tens of millions of years, that every once in a while an earthquake like this gets released.”
The largest historical earthquake in the cordillera of eastern British Columbia and western Alberta appears to have been on Feb. 4, 1918, at about 8:37 p.m., located about 150 kilometres north of Revelstoke near what is now known as Mica Dam.
Registering a magnitude of 6.0, the earthquake was reportedly felt as far away as Banff where pictures hanging on walls were reported to have moved. The event led to the collapse of two chimneys in Revelstoke.
