I don't have anything in my files regarding sailing through a volcano blast. For a really big one, I'd go with bare poles and trail a drogue.
On the positive side, the blast should strip off all the old paint and varnish, saving much elbow grease on a restoration project.
I like the anchoring idea. With an all-chain rode, you could probably get by with 5,000:1 scope.
Might not be practical for a 1,700 foot wave.
http://www.drgeorgepc.com/Tsunami1958LituyaB.html