This gives you a good idea of the aftershocks of the new earthquake segment. So this was not an aftershock of the M7.1, but was a clean rupture down the fault a way. I always thought the big earthquake was in fact made of some segments of this size, but they ripped in a fast sequence. That would account for the relatively low PGV for that earthquake.
It will be interesting to see the PGV of this one. There was massive soil failure, as shown by one of the helicopter shots. This is what Anchorage, Alaska will look like after their next big quake.
Will we learn anything from this earthquake? I sure hope they had put in a borehole accelerometer after the last quake, and some more instrumentation. The buildings so far look like the standard seismic death traps that always fail. On the aerial shots, the modern buildings did well. I'm waiting for the Japanese to come in and look for modern glass condos!
2 comments:
What do you consider "firm ground". Rock or stiff soils. What kind of N value would you assign to firm soils?
Dense sand, N value of 30 or more. This is the average at Chile, I think, and usually has a PGV amplification of 2 over solid rock, which should have P wave velocity of over 5kk/s, and S-wave of over 3kk/s
I think this stuff has an N-value of 10 or under, and I expect the PGV to be amplified 10 times or more. But who knows, they never measure this stuff.
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