Friday, December 6, 2013

Vancouver seismic plan related to Toronto


So, the big mistake at the beginning turned me off, but my good buddy Wayne encouraged me to look at it again.  I found some good stuff.

Now I know this plan, written by unpaid interns, probably cost the city a million bucks, but Toronto can just steal it.  The real cost is in doing all the pre-earthquake work in the plan.

At the same odds of 1 in 500 per year, Toronto has a different scenario.  That would be an M7 right under the west end of the lake, along the Hamilton fault.  Technically, that is probably an M6.5, but I find that scenario planning is only to 1 significant digit.  That was silly that Van picked 7.3.  Give me a break!  Really, you plan for 7, 8, or 9.  Ignore 5 and 6, unless you are a hopeless basket case, like Christchurch.

Toronto's 7 would have exactly the same effects as the Van 7.  There would be high PGV's on the soft-soil areas, and lots of liquefaction in High Park, etc.  Natural gas and electricity would be out, along with some big bridges which would have to be inspected.  Subway out, too.

Now, even if we were weenies, and only planned for an M6, there are some cheap things to do.  Seismic instruments speed up the inspection of important buildings, and bridges.  An M6 still leads to an extended power outage, but that should be planned for anyway.  It's the combined effect of both gas and power that is the killer, since many emergency power systems may depend on gas.

I just hope the Van plan shames Toronto into doing something.


Anonymous said...

So what ends up being the most stable terrain in Toronto (in the case of an earthquake), since it's all glacial deposit/lake sediment anyway? The older tills? Or anything with some clay in it, like the 2/5/9s from the Quaternary map legend, as long as they aren't too close to the water table? Me, I sit right in one of the 10 areas, which I guess isn't so good. It could be worse though; I could live near Queen's Quay...

Harold Asmis said...

Most stable is the heavy till. My young till probably has an amplification of 2. Heavy till means lots of swearing when trying to dig a fence pole. The condo down the road had to excavate extensively into rock, amp. 1. Probably no houses are on rock.