I have written a lot about this, and I have better terrain maps somewhere. I just noticed a lot of traffic with one of my old posts.
THIS IS NOT A SCARE STORY!!
I am not making any money on this, and we are talking long odds. However, this is a huge fault in the Precambrian, and I have lots of reflection seismic, and bottom sonar showing massive disturbances on the bottom of Lake Ontario.
This fault zone is has a lot of topography associated with it, so I think it pings off every 500 to 1000 years. That's about the same odds as New Madrid, but that last ping went off in historical times. This could have gone off a few hundred years earlier. The native translation of Toronto is not 'Meeting Place', but 'Mashing Place'. Those early explorers never did listen.
This fault zone is totally unstudied, except by me when I was at the old company, and actually doing things. It is so unstudied that Cleveland is getting lots of earthquakes because they are injecting into it. You shouldn't do that.
This fault has lots of earthquakes associated with it and they are probably activated by a slow change in the elevation of Lake Ontario, due to rising land at the outlet.
For long-odds earthquakes you don't panic, but you make slow changes to infrastructure, and emergency plans. They don't do that. If you look things up, then I have made some dreadful scenarios of an M8 on this fault. I don't want to be around for that.
So, in summary, this fault is as good as any in North America, but it is the most ignored.
ps. you can look it up in my posts, but basically, Ontario has about 5 of these 'mega thrust' structures. On the top of the hanging wall, the rock is all broken, and these are the areas of open-fracture limestone, deep valleys, etc. The footwalls are solid rock. Bruce Nuclear is on a broken hanging wall. Darlington is on a solid footwall.