Thursday, April 30, 2015

Nepal radar


Just did this in geosciences+  but I'll do it here.

Lots of tight fringes, like contour lines, is bad.  North of Kat the fringes reverse.  This is the super zone, or I like to call it the 'hammer zone'.  The whole valley is formed by the broken up hanging wall.  The maximum PGV or intensity would be in the hammer zone.  Step across to the footwall, and you find it much less.  However, precarious boulders and snowpacks are very sensitive to a few cm/s, so you lose both ways.  Firm ground motion in Kat was probably only 10-20 cm/s, but you would get soft valley amplification of 10 to 100 times.

In the hammer zone, PGV would be a few metres per second, which is enough to lift giant rocks.  In a similar earthquake in California, an entire cliff was lifted and you could only see it by some junk being sucked in.  Forget subduction zones, these things are our F5 tornadoes of earthquakes.

Further thought:  We should get a really nice image, just like this one, if our M6 thrust hits OK City.  :)  A bit smaller, but just as intense.

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