12 May 2010

Possible pre-failure ground deformation at the St-Jude quick clay landslide in Canada

Posted by Dave Petley

Sadly, it has been confirmed that the family reported missing in the landslide at Saint-Jude in Canada yesterday were killed in the basement of their house.  Interestingly, the area of road on the north side of the slide looks like this (this view is looking north, effectively standing on the slide looking across at ground that did not move):

Note the two large, very recent tarmac repairs extending right across the road.  The nearer of the two is very suspicious given its shape.  There are also other hairline cracks in the road – right in the foreground for example.  This one may have a small amount of displacement across it (the line is slightly offset) although this may well be just an artifact of the image.  However, compare the two repairs with the Montreal Gazette aerial view of the slide – in this case looking from the north towards the south (i.e. in the opposite direction to the Google Earth image:

 The larger of the two repairs is clearly visible in the image, which means that the lateral margin (edge) of the landslide is almost exactly where the other repair is located.  It may well be that slide was creeping prior to final collapse, although this is clearly no more than speculation at this time.

I am glad to see that the media reports are now calling this a landslide rather than a sinkhole!