Researchers solve seismic mystery that shook central Alberta communities

December 14, 2018 by Andrew Lyle, University of Alberta
Ice ridges on Lac Ste. Anne on Jan. 5, four days after a rare seismic event shook the lake. Researchers have solved the mystery of the cause: an icequake. Credit: Ryan Schultz/Alberta Energy Regulator

Icequakes created by a unique combination of weather and buckling lake ice—not earthquakes—caused the tremors that damaged homes and properties in several central Alberta communities last New Year's Day, according to new research.

"Central Alberta is a pretty seismically quiet place, so the fact that these tremors were felt in several communities across the region—and with this much power—is quite noteworthy," said University of Alberta geoscientist Jeffrey Kavanaugh, who worked with seismologists Mirko van der Baan and Ryan Schultz, and other researchers to solve the mystery of what caused the tremors.

"Unlike most , which is caused by tectonic stresses, these were caused by thermal stresses related to Alberta's cold climate."

The quakes occurred on Lac Ste. Anne, Pigeon Lake and Gull Lake, and had a magnitude of 2.0 on the Richter scale, recorded on the Albertan regional seismic network.

All shook up

Icequakes are pops and groans a lake makes as it adjusts itself during the course of the day.

"These are tiny little icequakes," said Schultz. "Usually this process happens slowly and as a series of smaller events, since can insulate some of the ."

But as New Year's Day dawned, a series of unlikely weather conditions came together to cause a much larger icequake, Schultz explained. A lack of insulating snow cover and a dramatic rise in temperature over 24 hours—from -35C to -5C—caused the ice temperature to rise rapidly.

"This caused a rapid thermal expansion of the ice, up to four metres towards the shoreline," said Schultz. "With nowhere for the expanding ice front to go, it eventually buckled and broke suddenly—resulting in the icequake shaking and the spectacular ice ridges forming near the lakefront."

Icequakes of this magnitude are very rare.

"Lake ice ruptured nearly instantaneously over hundreds of metres, which is very unusual," said van der Baan. "The last time this happened on Alberta lakes was probably several decades ago."

Schultz added it's possible that all of the conditions that occurred on that day only come together at the same time and the same place every few decades.

"But along these lines, better understanding the that caused these icequakes is helpful for understanding them and maybe even anticipating them in the future."

The study, "A New Year's Day Icebreaker: Icequakes on Lakes in Alberta, Canada," was published in the Canadian Journal of Earth Sciences.

Explore further: Fox Creek earthquakes linked to completion volume and location of hydraulic fracturing

More information: Jeffrey Kavanaugh et al. A New Year's Day Icebreaker: Icequakes on Lakes in Alberta, Canada, Canadian Journal of Earth Sciences (2018). DOI: 10.1139/cjes-2018-0196

Related Stories

2010 Chilean earthquake causes icequakes in Antarctica

August 10, 2014

Seismic events aren't rare occurrences on Antarctica, where sections of the frozen desert can experience hundreds of micro-earthquakes an hour due to ice deformation. Some scientists call them icequakes. But in March of 2010, ...

Measuring tiny icequakes

August 29, 2013

Measuring tiny icequakes is helping British Antarctic Survey scientists investigate ice streams despite the challenging environment they have to work in.

Ground shaking during devastating flood offers new insights

October 4, 2018

A devastating wall of water gushed down the Bhotekoshi/Sunkoshi River in Nepal on July 5, 2016. It came from a lake that had been dammed by a glacial moraine, but the dam broke and discharged more than 100,000 tons of water ...

Recommended for you

In China, a link between happiness and air quality

January 21, 2019

For many years, China has been struggling to tackle high pollution levels that are crippling its major cities. Indeed, a recent study by researchers at Chinese Hong Kong University has found that air pollution in the country ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.