The famous Oklahoma earthquakes had gone off a few years before. Although they rang church bells in Toronto, everybody laughed them off. What was unknown is that the creeping stress field from that zone had finally reached the Hamilton Fault, and was taking it to the edge.
Ten kilometres down, a small magnitude 5 earthquake was about to go. Normally, this would be almost unnoticed except by the crazy geophysics guy (He had just unchained himself, and headed for the hills), but this earthquake was special. For a thousand years water had seeped down to the fault, weakening it by chemical action. For a thousand years, the water pressure had increased because of glacial uplift, the drain of Lake Ontario being slowly lifted a few cm a century. The stress energies, caused by the high horizontal stresses, stored energy that dwarfed nuclear bombs.
This earthquake would remove the last linchpin holding the fault together. All the other 'hard spots' had been slowly removed by earthquakes over the centuries. The fault was 'locked and loaded', and all greased up with water.
With a bang, the M5 zone released. What would have normally ended at a distance of 300 m, broke out of its zone. It started initiating the final fault movement, as with every other earthquake of this type. A ring of dislocation spread out at the speed of sound in rock, making this a 'super earthquake', where the P-wave alone was enough to start shearing. At incredible speeds, the fault stared dislocating, in an oblique thrust. That was motion up the fault, and also to the North East.
-- that's it! I'm not doing any more. It's too scary! At least I saved the old guy. :)