Rare Manitoba earthquakes result of ancient rock movement

The cause of the two earthquakes this week is a common one, but rare in the Prairies.

When two earthquakes occurred on Wednesday near Spy Hill, Saskatchewan, Dr. Simon Pattison first thought they were the result of potash dissolving in groundwater, but he quickly learned that theory did not check out.

"I started looking at the data so it's like 'oh ok, that's kind of pointing towards something potentially something different, much deeper than the potash deposits," the Brandon University Chair of the Geology Department says Thursday.

Saskatchewan and Manitoba rarely have earthquakes. If they do, they are commonly the result of the potash movement and are small, but earthquakes of a 4.0 and 4.2 magnitude are rare for the area.

Pattison needed to look below the surface, 10 kilometres to be exact. After some digging, he has discovered the earthquakes are the result of something even rarer in Manitoba and Saskatchewan, but common across the world. 

"Basically, these earthquakes were triggered by Precambrian basement fault movement.  A classic type of intra-plate earthquake," Pattison explains Thursday night.

The movement of these ancient rocks caused the two quakes felt on Manitoba's southeast border with Saskatchewan.

"The epicentre-focus of these earthquakes is near coincident with a singular Precambrian basement lineament-structure in the Churchill-Superior Boundary Zone," Pattison says, pondering if the Precambrian basement lineament-structure could be a fault zone.