1) The Great Tokai Earthquake of the 21st Century

While not so bad for Tokyo (and probably Chiba, where I am, will escape severe damage), the Tokai earthquake predicted to hit Shizuoka prefecture anytime soon is a big worry for Japan.

The figure to the left is one of the major fault lines passing close to the mainland of Japan; the Nankai trough. It’s a subduction zone with the Philippine plate pushing itself under the Eurasian plate. The section marked A below is the one pertaining to the Tokai earthquake. It hasn’t ruptured for over 150 years (the last being in 1854), and is well overdue a predicted minimum M8 earthquake, centered somewhere in the Shizuoka prefecture.

If this one goes, which some scientists gave a 35-45% chance this decade, then it will cause massive destruction far worse than the Kobe earthquake of 1995. While Kobe was a different type of earthquake, and less powerful at only M7.4, it is useful as a comparison, noting that a 1 point increase in magnitude is a ~32x increase in power.

http://www.e-quakes.pref.shizuoka.jp/english/guide_01.html
http://www.jma.go.jp/en/quake_tokai/
http://geology.about.com/od/eq_prediction/a/aa_tokaiquake.htm
http://en.wikipedia.org/wiki/Nankai_megathrust_earthquakes

2) The Great Kanto Earthquake of the 21st Century

Not afraid of just one devastating once in a lifetime earthquake, well Japan has two lined up. Emanating from a related but separate faultline, the Great Kanto earthquake, affecting Tokyo rather more directly, is also overdue. In 1923 it killed over 100,000 people. Nowadays, while the deaths will probably be a lot less, the economic damage to Japan, and potentially the entire world, could be dire. There is an anime series on the subject of death in Tokyo by earthquake too. Check it out!

http://en.wikipedia.org/wiki/1923_Great_Kant%C5%8D_earthquake
http://www.animenewsnetwork.com/encyclopedia/anime.php?id=10704

3) Mt Fuji Eruption

Earthquakes? Meer shaking of the ground. What you really want for death and destruction is an active volcano. While not a very active volcano, the last eruptions being over 300 years ago, the constant threat is always there that eventually Fuji-san will get angry again and belch lava and ash all over Tokyo, prevailing winds coating everything to the east of the volcano. In fact, it has been reported that Fuji is overdue, and that its last eruption, in 1707, was two months after the great Tokai earthquake of that year. Although, it has to be said that the rip in 1854 didn’t set off Fuji, it’s a sobering thought that both might happen at the same time. What does that mean for Tokyo? According to the ash map, between 1-4cm of the grey stuff if the 1707 eruption is anything to go by.

http://en.wikipedia.org/wiki/Historic_eruptions_of_Mount_Fuji
http://news.nationalgeographic.com/news/2006/07/060717-mount-fuji.html
http://en.wikipedia.org/wiki/H%C5%8Dei_eruption_of_Mount_Fuji
http://www.japanprobe.com/2006/07/18/will-mr-fuji-erupt-soon/

4) Tidal Wave

Not content with its own natural disasters, the east coast of Japan could be affected by someone else’s problem. A magnitude 9 earthquake is coming to the west coast of America. The cascadia earthquake may generate a tsunami that will hit Japan and in certain places could cause, going from the past reconstructions, a 2-5m wave. Although this is a minor point compared with the devastation that will affect the US west coast’s major cities.

http://www.livescience.com/environment/050103_cascadia_tsunami.html
http://geology.about.com/od/quake_preparedness/a/aa_cascadiaEQ.htm
http://environment.nationalgeographic.co.uk/environment/natural-disasters/earthquake-technology.html

5) Bicycle death

Probably the most fearsome of the lot; crazy obaasan on bicycles. These lean, mean death machines combine two-wheeled destruction from behind with a near super-sonic battle cry. They are to be feared with a terror far greater than the combined power of the Kanto and Toukai earthquakes and Fuji blowing all in the same month (which could happen in theory).