Tuesday, August 30, 2016

Italian earthquakes at very low ground motion

They did have accelerometers at Amatrice, for which I am extremely grateful.  Here is a downloaded plot of horizontal velocity.

That gives a PGV of 20 cm/s.  I'm a big proponent that pgv is the universal measure of damage potential, since it is a direct measure of induced shear strain.  PGA doesn't represent anything in the physics world, since effects wildly vary with frequency.

I, and the Taiwanese, fight with everybody about this.  Our stupid engineers all go with shake tables and pga.  They are idiots, and that's why we are getting soft-story condos.

Anyway, 20 shouldn't do anything, only knock down piles of rubble, as we see in the pictures.  Or buildings with Maffie Concrete.  All our old brick buildings might be at this capacity, or maybe even 40 cm/s.  Our frame houses can take 100 before they kill us, although the region will have a billion dollar drywall bill at 60.

Most of the world is at 20 to death.  You can't be much lower and still stand up in the wind.  40 cm/s tilted the condos in Chile, but frame houses were untouched.  80 tipped the condos over.

ps.  5 will shatter all your precious knick-knacks, so secure them with seismic wax.  That level will also drop all the heavy books and trophies on your kids' heads if there are shelves over the bed.

pps.  Dear Starving Media people, and wannabe novelists.  I love being the guy who says "There's a shark in the water.", as long as nobody powerful pays attention to me.  As soon as the stupid people who run this place start to notice, I run into a deep hole.  :)  There are vested interests who build crap condos and nuclear plants.  I don't want to meet them.

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