The eathquake/tsunami/nuclear plant disaster that hit the Fukushima region was bad, really bad. But like many I believe you have an exaggerated perception of that event - not emotional impact, that was huge. But as for population, economic, infrastructure, etc., it was like a broken finger - temporarily crippling, and soon a distant memory. An eruption of Fuji would be much less critical, though still a disaster. The map below shows the expected ash fallout. It'll be a nasty day in Tokyo (62 mi away), with 1-2 inches of ash covering everything, but they'll clean it up. And, go look at a full map of Japan and see what a tiny geographic area the map below covers. Also, look at the OP - estimated cost of $1.6 billion - to a major industrialized nation, it's not that much. The USA spent 78 billion last year just on food stamps.