Canadian Fault Lines

[GoodSmeagol]

Recently here in Toronto Ontario we felt an Earthquake that hit about 75-100k North of Ottawa.
I was talking about it and expressed my belief that there were no fault lines in Ontario. I was corrected and told there are lines along the St Lawrence and through Niagara Falls.
Googling it has not answered any questions as to why I have never heard of this fault line, in fact I can only find a slight mention of it on one map.
Does any one know about these lines, and any articles on them?
Thanks

[Thinking Aloud]

I know it's Wiki, but there's an article on it here with links to a couple of seismic zones in the area. These kinds of zones, in the middle of continental land masses aren't necessarily associated with major fault lines, but can just be areas of local relative instability, comprised of a myriad of minor faults.

Fault lines riddle the crust all over the place, but most aren't active, and some can be very old indeed. The Great Glen fault in Scotland (the one along which Loch Ness lies) formed before the Atlantic Ocean opened as part of a previous continental collision event - the other end of it is somewhere in North America - but was split by the Atlantic rifting. The line of weakness still produces occasional tremors however.

Big faults like the San Andreas are generally found on plate boundaries, where sections of the Earth's surface rub against or push underneath one another.

[Thinking Aloud]

Further to that, it looks like there's a very old rift system (the Midcontinent Rift) in the Great Lakes area, with another half it's age (the St Lawrence Rift). These events would have produced weaknesses that could easily still be present today.

[Gawdzilla Sama]

That Scots character on Discovery Channel mentioned the St. Lawrence was a fault, IIRC. And there was opposition to building the Seaway because the fault might "become active during construction". (The real reason for the opposition was the fear of the RN bombarding Chicago, weird as that sounds.)