Japanese Earthquakes

Which of the four main islands would be the safest during an earthquake? and why

There are trivia books published of Japan that lists things like by region such as meat consumption or ramen preference. Anyway, the most recent one we have shows forecasted earthquakes by region and it appears that most of Shikoku and Honshu have 6-26%+ chance of the next big one hitting there within 30 years. Hokkaido is roughly 1-6%, and Kyushu was roughly 1-3%. So based on this (really unreliable science of forcasting earthquakes) I'd say maybe Kyushu is your best bet of avoiding the next big one.

In terms of destructive power, there is no way to know where you'll be safest, it just varies on way to many factors. Most people get hurt by falling objects, so you'd probably be safest under a table in the middle of a wide open field on any of the islands equally.

The safest island would be the one furthest from that particular earthquake.

When earthquakes strike they affect the area closest to the epicentre, and then depending on the size of the quake, they may also be felt further away.

For example here in Tokyo we felt both of the large earthquakes that have hit Niigata in the last few years, but just as a gentle swaying, In Niigata however there was substantial damage. A smaller earthquake in Niigata wouldn't be felt in Tokyo though. Earthquakes are relatively localised events, they are not felt in the whole country simultaneously.

Earthquakes in Hokkaido are not usually felt in Tokyo but they may be felt in the north of Honshuu. An earthquake in Tokyo would be felt in other parts of Honshu but not on the whole island and probably not on the other islands. An earthquake in Kyushu will be felt in Kyushiu but probably not on the other islands.

The question you might be wanting to ask is "where in Japan is least earthquake-prone"? Niigata for example is obviously quite prone to quakes, and Tokyo has been hit many times and is currently waiting for the big one. The Kansai area (Kyoto, Osaka) is thought to be less earthquake-prone, but then was hit by the huge Hanshin earthquake in 1996 which severely damaged Kobe.

You really have to just take your chances with earthquakes if you want to come to Japan- you can make yourself a bit safer by living in a newer building which has some measure of "earthquake proofing", but nobody knows where or when the next "big one" will be.

The last 3 times I've been in Tokyo there have been small to moderate earthquakes. The largest was M4.7. If you are concerned about being in an earthquake then read up in advance on what to do when the shaking starts. The vast majority of quakes will be over before you can even act. Even the M4.7 lasted only about 5 seconds and there was no damage reported. The chances that there will even be an earthquake while you are visiting is slim. I have been all over Japan and never felt one except for the Tokyo quakes.

Actually the larger ones tend to last longer, giving you time to act. The biggest one I have felt was about 3 years ago in summer, when a quake of about M5.6 occurred directly below Tokyo. We had time to blow out candles that were burning and move away from the large mirror we were sitting next to (it was a dance studio) as it lasted about 30 seconds. Larger earthquakes can last several minutes but apparently if the shaking is severe it can be impossible to stand.

Here is a link with info on what to do if a large earthquake hits:

http://www.fema.gov/hazard/earthquake/eq_during.shtm

I recommend visiting the fire departmen in ikebukuro station, that has an earthquake simulator (bousaikan). You can watch a 3D movie about earthquakes, practice to use a fire extinguisher, crawl through a room full of smoke and... experience a M7.0 shaking while trying to hold on to a table. It's fun! ;)