Calgary, a prairie city far from any nearby fault lines, felt an unfamiliar sensation early Tuesday evening — an earthquake.
A 6.5 magnitude quake occurred at a depth of 10 kilometres near Challis, Idaho, at 5:52 p.m. MT, and was felt in Calgary just a few minutes later.
The epicentre of the quake was nearly 700 kilometres southwest of Calgary.
Tom Sampson, chief of the Calgary Emergency Management Agency, tweeted that the lights swayed in the city’s emergency operations centre — where his team has been busy since the city declared a state of local emergency to respond to the COVID-19 crisis.
John Cassidy, a seismologist with Natural Resources Canada, said the earthquake was a large one, and was felt in southern B.C., Montana and Utah as well.
“The shaking in Canada is not particularly strong, it certainly isn’t damaging shaking, but it certainly was noticeable by many people,” he said.
At great distances, typically what you feel are what we call surface waves. These are almost like waves on the ocean … those waves are relatively slow, and they are the kind of waves that can get high buildings shaking, so high rises will tend to sway back and forth during these types of earthquakes.”
Cassidy said it’s been decades since Idaho last experienced a quake of this size, but its not extremely unusual for the region. He said globally, there are about 120 earthquakes of that size each year.