Theory on loud bang - not rock solid!
Were conditions favourable for frost quakes Friday? Here's a look at the temperature profile prior to the event.
Published Monday, January 30, 2017 11:47AM AST
Last Updated Monday, January 30, 2017 11:48AM AST
At about 1:50 Friday afternoon, residents of northeastern New Brunswick felt the earth move. By midafternoon, posts about a rumble and a loud bang had taken over my Facebook page. I decided to asked people where they were when they heard/felt the event. 146 comments later, people from Atholville to Salmon Beach and across to New Carlisle Quebec posted their stories.
After reading the comments, I looked into the possibility of an earth quake in the region. Experts tell us there was no seismic activity in that area Friday afternoon.
So what then? Frost quakes perhaps? By definition a frost quake or cryoseism is a seismic event caused by a sudden cracking action in frozen soil or rock that is saturated with water or ice. As water drains into the ground, it eventually freezes and expands, putting stress on its surroundings.
In order for a frost quake to occur, certain conditions must be met:
-saturated soil: in the winter, that would imply a thaw or mild spell with rain.
-little insulation: not much snow cover in place.
- a rapid, significant, drop in temperature
Friday, we could check the first 2 off that list, but the temperature drop didn’t seem to be significant enough for this kind of activity. It was +2 on Thursday, so the ice and snow likely did melt and saturate the top layer of soil, but the 12 hours leading up to the “events” only saw the temperature fall from -3 to -5. Was that enough? Not usually, but soil type needs to be considered here. Geologically, areas of permeable materials like sand or gravel, are more susceptible to frost action, and are likelier candidates for frost quakes.
Personally, I’m leaning towards the frost quake theory. The conditions were not “text-book”, but certainly could have triggered the earthquake like rumbles that had everyone talking in northeastern New Brunswick last Friday.