Tuesday, February 3, 2015

New USGS Seismic Hazard Map

I really hate to make fun of these things, since they are all-important and created by God-Kings.

Here goes:  What is it?  It is a map of Chance.  If you were to throw an Earthquake Dart at it, the redder zones would have a magic attraction, making it more likely that the dart would land near there.  It doesn't have to.

What are the units?  Honestly, all this futzing is only good to 1 digit (log or decade), but everybody likes to quote to 1 percent.  Epic battles have been fought over the exact placement of a line, sort of like climate science.  The Big U only works with acceleration because that's what they do in California.  I told them a million times that it doesn't work in the East, but do they listen?  :)

Even if you used the right units, (PGV), there is the question of what ground conditions.  You might want to uniformly use base rock, but the Miss. Valley doesn't have a rock in sight.

What is it good for?  Not much, since every dang small town has its own building code.  In Canada it is a bit more rational.  For example, they've bumped up Oklahoma.  Are they now going to put more nails in the framing?

But it is a pretty map, and totally centred on historical earthquakes.  Enjoy.

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