Since it is coming up in a couple of weeks, maybe incorporating some of the techniques fron "The Great Shake Out" might show how school districts etc are preparing in the Mid West US along the New Madris fault:

http://www.shakeout.org/centralus/

It has some good K-12 resources that might provide a framework for age appropriate conversations with even a 7 year old.

http://www.youtube.com/watch?v=6Rjyt7XAZrA&feature=player_embedded#at=50