We've had a number of small earthquakes in the area in the last couple of hours, the largest being a 4.3 or so. The interesting thing is that the phone app I have announces them before or as they hit. Months ago there was a stronger one for which the app gave me a solid 5-6 second warning, and it showed the countdown to when it would hit my location, which was accurate, but by the time it got to me it was barely noticeable.

I've also checked out the possibility of an earthquake setting of an eruption on Mt. Fuji. Apparently it's a real possibility, and IMO the greatest natural threat to this area. A Mt. Fuji eruption would shut down all of Tokyo for weeks.

Remember the Iceland eruption of 2010? It shut down all sorts of air traffic for weeks. I actually met a guy at the pool in Pingtung who was stuck in Taiwan because of that eruption. And that was in Iceland. Can you imagine a major Fuji eruption?