August 24th, 2011

SF City Hall 1906


The interesting thing about the crowd in front of 40 Wall Street in New York City after yesterday's junior earthquake is that, if the 5.8 had actually been a fore-shock of a larger quake, they were in greater danger standing in front of the building than they'd have been if they were still inside the building. New York's skyscrapers will withstand fairly large earthquakes because steel-framed buildings have some inherent earthquake resistance (the city's masonry buildings are at considerable risk, though, as masonry construction has to be specially designed to deal with seismic events.)

But while most of the skyscrapers of New York will come through any fairly large earthquake mostly intact, the same can not be said for their windows or their exterior decoration. Had a larger earthquake struck while that crowd was milling about, they would have been exposed to falling chunks of stone and terra cotta, not to mention shards of glass from shattered windows. A narrow street in front of large buildings is one of the worst places to be in a big earthquake.

Most people's instinct is to run outside when an earthquake hits, but that's dangerous. Even in an old masonry building, you're probably going to be safer riding it out indoors, as long as you stay away from glass and heavy objects that aren't secured to something. Masonry buildings are considerably more likely to lose their facades into the street than they are to completely collapse.

A forest is a pretty bad place to be in an earthquake, too. A strong earthquake can snap trees as though they were matchsticks. During an earthquake I think I'd rather be in a large city than in this neighborhood. You just can't get away from the trees around here.

This earthquake map that Brad DeLong posted yesterday is interesting. The Pacific Rim has been so active of late that it looks like a seismic goatse.