Mystery of New Year’s Day quakes explained

Strange seismic activity called ‘icequakes’ shook central Alberta residents

EDMONTON— A group of scientific investigators finally put to bed a cold case that shook lakeside communities in central Alberta early this year. Close to midnight on New Year’s Day, the Alberta Geographic Survey picked up a series of seismic events, smallscale, earthquake-like activity, registering 2.0 on the Richter scale at Gull Lake, Pigeon Lake and Lac Ste. Anne, all within a 150-kilometre radius of Edmonton.

The days that followed saw residents near those waters reporting booms and quakes that woke them up that night, and strange ice ridges forming along shorelines.

After reviewing the reports, Mirko van der Baan, a physics professor at the University of Alberta who aided in the investigation, said he had never seen anything like it.

“When we looked at it, we were surprised because we didn’t completely understand what had caused it,” van der Baan said.

The inquiry that followed had him working with a team of scientists, including minds from the University of Alberta, Western University in London, Ont., and the Alberta Geographical Survey, which took measurements and compared the results to similar cases documented around the world.

“Of all the things I’ve ever worked on, this felt the most like detective work,” survey seismologist Ryan Schultz said. Working with leads reported by residents who documented the damage, the months that followed saw the scientists put their heads together to construct a story and find the answer.

Published in November in the Canadian Journal of Earth Sciences, they determined that the lakes were the sites of “icequakes,” a phenomenon where rapidly expanding ice with nowhere to go buckles, breaks, and pushes outward.

Icequakesare not uncommon, Schultz said, often occurring on a scale too small to cause concern, or even trigger seismic sensors.

“You hear the pops and groans that happen on lake as it heats up during the day … these are little icequakes,” he said.

But that event that began on New Year’s Day, he added, was one of the largest events of its kind ever reported.

“This is basically one of those smaller icequakes happening in a bigger, quicker way.”