Not as bad as you think?
Did you happen to notice the big fuss over the twin towers going down?
Now times that by a city of buildings, some bigger, some smaller, and all of them destroyed, then you tell me its not as bad as you think.
90% of the US is a big deal. Hopefully it won't be happening in my lifetime, I've also heard of another natural disaster that involves a mega tsunami striking eastern US, but that's unrelated to the subject.