Tuesday, December 9, 2008

SRL - Southern Ontario Polaris Sites

I got my new Seismological Research Letters, from the BSSA. I think some of these articles are on their site. This membership is my only vestige from my former scientific life, and is one reason why I blog for money.

The article that I like is all about my baby, the seismic network in southern Ontario. When I was rich and famous, I bent all sails to the wind to get this started, and funded from the old company. With me gone, even though they are trying to build a new nuclear plant, I wonder how it will survive, especially since the general attitude of the current leaders seems to dismiss all seismicity (floating nuclear plants?).

In this paper, they look at the site response of various sites. Ideally, you want your site response to be very flat, which means that no particular frequency is being amplified. If, however, you know the site response, you can remove this effect. The big problem comes if you are assessing damage, and you have no idea of the site response. As I have said before, if you are in a river basin, on soft clay, the amplifications can be 10-100 times!

As we see here, nearly all the stations have a very flat site response. That's because we made a lot of effort to find sites on hard till, which is nearly rock as far as seismic waves go. The main exception is our TORO site, which is on recent landfill out on the Leslie St. spit, which goes way out into Lake Ontario. Nevertheless, this is a good site location-wise, since it covers the Toronto area, and we could not find any good locations near the city, since the urban rumble was over-powering.

All of these sites have really good seismometers, which will act as strong ground motion sensors, should we have our expected earthquake. The clock is ticking for our large Toronto earthquake, and I'm always amazed that it seems to be 100 years late!

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