Will a monster tsunami hit Tokyo soon?

The worst-case scenario is horrifying. Waves swamp Haneda airport and hurl freighters into Shinagawa office towers. Kawasaki chemical factories explode into toxic fires. Walls of water moving at jet speed pulverize, mangle or gut buildings and rise up to the fourth floor of the Japan Times in Shibaura.

The tsunami rushes up the Edo, Arakawa, Sumida, Tama and Meguro rivers, past Naka-meguro and into the bowl of Shibuya. The reclaimed lands of Ota, Minato, Chuo and especially Koto wards -- already below sea level in places -- become an uninhabitable swamp, setting the economy back decades.

As unbelievable as it seems, that’s the Tokyo equivalent of what happened to Rikuzen-takata, Kesennuma, Minami-Sanriku, Ishinomaki and about 50 areas along a 500-kilometer swathe of Japan on March 11.

In those areas, indented coastlines -- which closely resemble Tokyo Bay from the air -- pushed tsunamis up 10 meters higher than in other areas.

But could it happen here, in the world’s biggest city?

“Researchers are now investigating what could happen here,” says Yuichi Kogasaki, director in charge of the Tokyo Metropolitan Government’s disaster prevention division.

“Until recently, we never expected that such a big tsunami could happen in Tokyo. But now we realize the need to review all our master plans.”

Damage estimates

The city’s previous study in 2006 estimated a 7.3 quake in “north Tokyo Bay” could kill between 5,600 and 7,800 people, injure 160,000, trap 22,000, damage about 500,000 buildings, spark at least 300,000 fires and force 4 million people to evacuate.

Even the March 11 quake, though far from Tokyo, caused liquefaction in Urayasu, set fire to fuel drums in Odaiba and Chiba and disrupted the supply chain.

“We’re prone to disasters more than other cities, so we have to be prepared better than other cities,” says Kogasaki.

Most officials and experts admit that Japan was prepared for an earthquake, not a tsunami. But calling the disasters “unimaginable” or “a thousand-year event,” as many did, ignores geological history and Japan’s connection to the Pacific Ring of Fire, where an 8.8 magnitude quake hit Chile last year, and a 9.1 off Indonesia killed 230,000 in the 2004 tsunami.