There used to be a site, one of the survival sites, where you could map a blast. While the site is still there, you can no longer put in your own coordinates. About 3 years ago you could still input information because I remember putting in downtown San Diego to see how far the fallout would come. Wish they hadn't removed that feature ;<
There is a site- called "nuclear terrorism". You can create maps of what a nuke strike would do in your particular location. I don't have the url- will look.