According to this article, a Japanese scientist thinks that a big earthquake (magnitude of 7 or more) is likely to hit Tokyo today or tomorrow.

The last big one in Tokyo made 120,000 casualties in 1923. Even if building are surely stronger than 80 years ago, they would probably not resist a magnitude 8 earthquake.

This article has a sentence that I don't like very much: Officials and scientists agree that Tokyo is overdue for a huge earthquake.

The good news is that I go to Singapore tomorrow morning, for one week ;-)

Just in case you feel not ready, you better should read this survival guide and this one... This cannot hurt, at least (some kind of Pascal's Wager!).