Earthquake near Rocky Mountain House Saturday one of dozens detected in Alberta so far this year

Earthquake near Rocky Mountain House Saturday one of dozens detected in Alberta so far this year

A 4.3 magnitude earthquake that struck near Rocky Mountain House Saturday morning left many wondering how and why this natural event could occur in landlocked Alberta. Turns out, they are fairly common in our province — we just don’t usually feel them.

The quake, which left some residents of Clearwater County without power for about two hours and forced a gas plant off-line as a precaution, is one of dozens of small earthquakes that occur in Alberta every year, Geololgical Survey of Canada research scientist Honn Kao said.

“Alberta is not technically free of earthquakes,” Kao said. “The distribution of earthquakes in Alberta is not uniform, but they tend to be much more frequent along the Alberta British Columbia border.”

Of the 86 minor earthquakes measured in Alberta so far this year, most of them happened near Jasper and Rocky Mountain House. This is because active tectonic plate movement beneath the earth’s surface builds the mountains, and the release of this force causes the earth to rumble. Over the years, these mostly innocuous temblors actually make our Rockies even more magnificent, raising their height anywhere between a couple of centimetres to a few metres depending on the size of the earthquake.

Most of Alberta’s earthquakes average a magnitude of less than three and aren’t felt unless you happen to be directly above the epicentre, the area on the Earth’s surface directly above where the earthquake occurred. Fatalities or property damage aren’t usually caused until a quake reaches a magnitude of 5.5 or six.

There were no injuries or structural damage reported from Saturday’s earthquake.

“The beauty about yesterday morning’s earthquake is that it’s big enough to feel it, but not big enough to cause significant damage,” Kao said.

Big earthquakes happen when a large amount of force accumulates in the tectonic plates over time and is released at once. But this is very rare in Alberta. Tectonic plates move only between two and four centimetres offshore of western B.C. each year — equivalent to the growth rate of your fingernail.

“Generally speaking, they are always small (in Alberta,)” Kao said. “If you compare to B.C., the chance of a big earthquake is definitely much smaller, there’s no doubt about that. But because the tectonic force is there, there’s always a risk.”

Research shows man-made activities can induce earthquakes, though debate still exists on the issue, Kao added. Damming and hydraulic fracturing used in the oil production process increase production but can also induce earthquakes, he said.

Despite the statistical rarity of a serious earthquake in Alberta, Kao said Saturday morning’s earthquake is a reminder that residents should do their best to prepare themselves for the possibility of a larger quake. This includes simple measures such as securing furniture and removing glass from high shelves.

“This is a perfect example for residents to realize they need to take this opportunity and be prepared just in case a damaging earthquake occurs in the future,” Kao said. “It’s generally the public’s impression that Alberta seems to be immune from earthquake activity, but that’s not true.”


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