Smaller Nankai quake also dangerous

Kyodo

A temblor with magnitude of 8 in the Nankai Trough off central and western Japan could heavily damage high-rise buildings in Tokyo and Osaka, a national research institute recently said.

While it has been predicted that a Nankai Trough quake could reach a magnitude of 9, the study by the National Research Institute for Earth Science and Disaster Prevention in Tsukuba, Ibaraki Prefecture, shows that smaller quakes may also cause heavy damage.

The institute examined construction data on buildings as high as 30, 45 and 60 stories.

An magnitude 8 quake will not cause such buildings to fall, but their floors would be seriously deformed and rendered off-limits, the study said.

In an M8.6 quake, 30- and 45-story buildings near the Tokyo Metropolitan Government Building will be badly damaged, with 30-, 45- and 60-story buildings in Maishima in Konohana Ward, Osaka, near Osaka Bay, taking similar damage.

In Nagoya, 30-story buildings near the Aichi prefectural office could also be badly affected by such a quake.

But possible damage will depend on how they were designed, the institute said.

The Nankai Trough runs from Suruga Bay in Shizuoka Prefecture to Hyuganada off Miyazaki Prefecture.