Saturday, January 5, 2013

Alaska earthquakes fill in zone

Now, I just can't get more than 30 days plotted on a map without actually doing work.  However, a few of the old earthquakes show up.  The aftershock lengths are exactly the same.  We don't really expect that middle zone to fill with another M7.5 because after a few of these we expect the big M9 to rip the whole length.

Notice that I have been going on and on about the earthquake chatter that shows the slab is on the move. Yet this earthquake didn't have a speck of indication.  That is because it is 'glass smooth', as one would expect for a very active zone.  In my model of fault mechanics, the fault was under high stress with a very low critical displacement - dc.  As I've said, this was a 'bathtub quake' since it resembles your foot in the water on an old tub.  Very high friction while still, giving you a false sense of confidence.  One fraction of a mm of movement, and whoops!  There you go!  That's dynamic friction!

After this quake, I expect the chatter on the slab will increase, but that zone is still in a stress shadow from 1964.  I think our M9 strike-slip here will happen before the M9 there, but I wouldn't hold my breath.  Still, this 'Marching Earthquake' happened a lot sooner than I would expect, after the M7.7.  Perhaps some more M7+'s before the 9?

*Italian disclaimer - You will notice that 'real' seismologists don't touch all this action with a bargepole.  These things usually work to a different time scale than measly humans, so DON'T PANIC!

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