View Single Post
10-10-2012, 04:33 PM
The Gal Pals
Join Date: Oct 2006
Originally Posted by
I don't see why people are startled by this minor earthquake. Montreal witnesses earthquakes between 3.5-5 almost every 5 years or so and lesser ones each day, 99% of them are never felt.
The Valley of the St-Lawrence river lies between two mountains chains: the Laurentians and the Appalachians which were formed years ago by volcanoes and tectonic plate convection and movements. Many ancient fault lines are too be found along the river reminiscent once of the different plates which were colliding once and producing heat. This heat melted rocks and created mountains which in form erupted, releasing magma and forming the igneous rocks of the Canadian Shield (Northern Quebec and the Laurentians mountains). These inactive fault lines can become active sometimes triggering minor tremors like the one we witnessed today after midnight. The Charlevoix region in Quebec, for example, can see earthquakes of up to 7.
The soil in the Valley was also compacted by years of glacial erosion. The land tends to lift which also causes minor tremors. Mont-Royal for example, is a volcanic intrusion caused by the uplift motion of the soil.
Montreal and the St-Lawrence Valley is the second most active seismic zone in Canada after BC. Tall Buildings in Montreal are designed to withstand earthquakes of 6-7 magnitude.
I was under the impression that most Quebec earthquakes were the result of isostatic (or post-glacial) rebound.
And I don't think that Charlevoix has ever experienced a 7.0 magnitude earthquake. Especially not in recent memory - you'd probably have to go back hundreds of years. If they did, almost the whole province would feel it and that area would be close to devastated.
The Gal Pals
View Public Profile
The Gal Pals's albums
Find More Posts by The Gal Pals