Friday, August 7, 2009

Shake, rattle and roll (Why so few Japanese pagodas have ever fallen down)

This economist.com article begins:
What has mystified scholars over the ages is how these tall, wooden buildings cope so well with the earthquakes and typhoons that plague Japan. Many have been struck by lightning and burned to the ground. Others have been torched by marauding warlords. Fire was a perennial hazard in Japan when wood and paper buildings were the norm. But, remarkably, only two of the country's hundreds of wooden pagodas have collapsed over the past 1,400 years as a result of violent shaking.
The article points out that the eaves of the pagoda extend the buildings' width 70 percent while those in China only extend 20 percent. This longer extension protects the ground from the large amount of rainfall Japan sees every year, which in turn protects the foundation.

This might explain why "the disastrous Hanshin earthquake of 1995 killed more than 6,400 people, toppled elevated highways, flattened office blocks and devastated the port city of Kobe. Yet the magnitude 6.9 shock left the magnificent five-storey pagoda at the Toji temple in nearby Kyoto unscathed, even though it levelled a number of lower structures in the neighbourhood."

Earthquake prone areas might take a hint from the Japanese pagoda and incorporate some of the unique characteristics when building.

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