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!