Thursday, April 24, 2014

Seismic Hazard and Risk for Vancouver

It occurred to me that Vancouverites might choke on their collective high fat and sugar breakfasts before their morning commute, when they read my 'predictions'.  This should not be the case.

 Geologists who want to make money for their organizations tend to go to the glorious big faults.  In California they believe in thin straight lines as the be-all of seismic hazard.  This was carried to the extreme by the Global Gorming crowd.

Sad to say, this is not reality.  The boring truth is that seismic hazard is a big ugly smudge, and no individual earthquake or 'discovered' fault is going to budge it.  The smudge is caused by overwhelming uncertainties.  It is just as likely that the most damage for Vancouver will come from a local M6.5, a la Christchurch.

So, if you are living in a big pile of bricks on a swamp, then the good news is that your insurance is under-priced by a factor of 10.  Top up on it, to leave money for distant relatives.  If you are on that BC hardpan that takes blasting to dig a foundation, then your fish tanks are safe, and you can keep that champagne glass fountain you set up at New Years.  

Those that live near the coast better keep running shoes handy, and watch those bridges.


Anonymous said...

Regular reader of yours here. Is the Vancouver hardpan you speak of bedrock? Is the georgian Bay shale here in Toronto, although not as solid as granite, just as stable in an earthquake? In other words, how would all of our downtown condos here in Toronto do in an M7?

Harold Asmis said...

Yes, hardpan is equivalent to rock, which is the same as our heavy till (shovel bouncer), or the shaley limestone. All our big buildings are in this stuff, but they are now building with transfer slabs, and soft stories. I think when we have our M7 in Toronto, in 1000 years, these will be damaged. :) If you own a condo and can get total investment insurance at less than 1/1000 per year, you should get it, for these soft story things.