I think the Canadians had it at M4.5, but the USGS puts it down to an M3.9. That's more likely since there appears to be no significant PGV. This was just a damp squib!
It's at a beautiful spot, right at the triple junction of the failed rift. This area is capable of producing large earthquakes, and Montreal won't take it very well, what with all the Mafie concrete.