Alberta’s strongest earthquake in a decade shook the ground near Rocky Mountain House early Saturday morning.
A 4.3-magnitude earthquake struck at 9:28 a.m. about 27 km southwest of the town. It was initially reported as a 4.1 magnitude quake but later upgraded.
While there were no reports of significant damage or injuries, there was a whole lot of shaking going on around.`
In Strachan, about 25 km southwest of Rocky, Pat Haupt, heard what she described as ‘a roar.’
“The house started shaking,” said Haupt. “The china in the cabinet started clattering and that lasted about six seconds and all of a sudden it felt like a bulldozer hit my house.”
The power was knocked out for about 500 residents and businesses in Clearwater County from Caroline to Nordegg including the Strachan Gas Plant. The Keyara Corp. operated plant flared off excess gas when it lost power but there was no damage or reported injuries. A substation in the area locked out to prevent a surge or other damage to the system a couple hours later.
Ted Hickey, Clearwater County’s director of community and protective services, said there was no risk to the public. He said the county also received many calls about the quake but there were no reported damages.
Honn Kao, an earthquake seismologist with the Geological Survey of Canada, said an earthquake of this size typically is big enough to be detected by residents but does not cause significant damage. Kao said people do not typically feel an earthquake when a magnitude is below 2.5 unless they are right on top of the epicentre.
“There are quite a few earthquakes in the region usually to the west in the Rocky Mountain area,” he said. “Most of these events are not really big enough to be felt. This one was certainly big enough to be felt.”
The centre received about a dozen or so “felt” reports from area residents. While natural quakes are common in this seismic region, there hasn’t been an Alberta earthquake this big since 2001 when a 4.0 quake shook an area northwest of Rocky Mountain House close to the B.C. boundary.
In the last 30 days there has been two earthquakes in southern Alberta with a magnitude between two and three.
Kao could not say for sure what caused Saturday’s quake. Oil and gas activity has not been ruled out as a potential cause.
“This particular region is not immune to natural earthquakes,” said Kao. “We have plenty of evidence that natural earthquakes (occur here) and there’s also possibility of induced (quakes) but unless we actually look at the parameters and local operators and compare with what we have observed, it is very difficult to determine at this point.”
Kao said this earthquake should serve as a reminder for residents living in seismic zones to be prepared in case of an emergency to mitigate the risks.