Friday, August 26, 2016

An Italian earthquake in Toronto

Every few years an M6 earthquake hits Italy.  At the epicentre all the buildings fall down and kill everybody.  Yet, for any given location, an earthquake only hits every 500 years.  So, all those people are dancing in the streets like the little pig with the straw house.

I have decided there is a 'sweet spot' at the 1 in 500 per year probability, where you  have the most deaths. At the 1 in 100 years, you have living memory and everybody builds better, like California.  As well, all the old buildings from a 100 years ago have been already knocked down in the last earthquake.

Every single disastrous  earthquake has been at these odds, yet nobody does anything.  I'm just picking on Toronto for now, but it goes for every city.  Basically, officials always think that if it is out of living memory, it can never happen.  We'll call this event an M7, although it could be 6.5.

Toronto is like every Italian hilltop village.  Why worry?  Why do anything?  The only way to get people concerned is to lie through your teeth, and say if Vancouver hasn't had an earthquake for 300 years, it's going to happen tomorrow.  In reality, they are still at the same odds as everybody else.  There is no master clock that ticks down.

Vancouver is lucky that the Japanese were around to record the earthquake.  In India, because of the wars and such there are no ancient records of earthquakes.  The Chinese have some old records.

If you look at the lake sediments, you can see that this type of big earthquake is a regular thing for Toronto, yet we have not had the benefit of Japanese record keeping.  Ignorance is bliss.

Thursday, August 25, 2016

Time to move all of old Toronto onto deep piles

Reference



It's not that difficult.  Obviously this building will be placed on deep piles because of the subway.  It will then remain functional through any type of earthquake, including our 'upcoming' M7.  It's more important for buildings on soft soil, which will be disrupted even for the Oklahoma M7.  Downtown Toronto has just taken pieces of the old brick buildings and put them in steel frames for new buildings.  But no building codes addresses the functionality of the building after an earthquake.  Piles offer a factor of 10 to 100 in pgv seismic ruggedness especially related to functionality.

Of course, this also applies to what Torontonians refer to as 'real seismic zones'.

Wednesday, August 24, 2016

Small Italian earthquake with big consequences





This is the standard earthquake that is expected all the time along the spine of Italy.  The PGV was probably 20 cm/s, which any rugged building should survive.  But all the buildings here are piles of rocks.  Thus is the consequence of no seismic capacity.  Such beautiful, ancient towns, no chance to knock them all down and put up something with the more 'normal' capacity of 50 cm/s.

We'll continue to see this every few years.  The above plot of 'estimated fatalities' takes into account the construction.