Friday, March 25, 2011

Japan Earthquake - Quaternary Geologist's Take


I'm not writing anymore, since I realized there was a tv show that told you everything you need to know about global tectonics.  I like the part about Southern Ontario.

Southern Ontario on the other hand, occupies a so-called 'intraplate' setting, a safe place it was then thought when our nuclear plants were built decades ago in the absence of any fundamental knowledge of the faults that lie directly below Pickering or how Canada's geology had even been put together. Some geologists speculate that a large break (rift) in the crust lies below Lake Ontario connected to the dangerous St. Lawrence Rift which underlies the Ottawa Valley and St. Lawrence River extending as an arm down the Hudson valley to New York. Moderately large damaging earthquakes occurred in 1732 (Montreal; M5.8), in 1935 (Timiskaming; M6.2) and in 1944 (Cornwall, Ontario - Massena, New York; M5.6).
The last was Canada's costliest with considerable impact on urban infrastructure. Large landslides in the Ottawa Valley and active faults below the floors of lakes in the northern reaches of the valley again indicate large prehistoric earthquakes. As geologic research moves forward, so the 'recurrence time' of such earthquakes steadily shrinks. A magnitude 7 earthquake every couple of thousand years is now suggested. But when was the last? Do we know the full population of faults below our towns and cities? Do we know enough about how local rocks and sediments behave when shaken?

Eyles was a chief proponent of the 'Fault Under Pickering' camp, which our drilling and deep geophysics tended to wipe out.  That was the last research done in this area.  I see he can't leave it alone, but I agree that it is almost criminal to consider new reactors without a speck of new work for geology.  I wish he would show up at the Darlington hearings; and because he is so powerful with a tv series and all, I will say:  "Yes, there is a big honking fault under Pickering (more or less)!

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