How japan’s oldest wooden building survives giant earthquakes

Japan has been struck by magnitude 7.0 or greater earthquakes a staggering 46 times since the pagoda at the Horyu-Ji Temple was built in 607AD. So, how did the 122 foot tall structure stay upright through all that shaking?

Multi-story pagoda technology arrived in Japan during the sixth century alongside Buddhism from China. On the mainland, pagodas were traditionally built of stone. However given Japan's seismic instability and higher annual rainfall, that design was simply untenable. But, after much experimentation, Japanese builders figured out how to adapt them to the shaky conditions through three design changes: the use of wide and heavy eaves, disconnected floors, and a shock-absorbing shinbashira.

Japan is a wet country with roughly double China's annual precipitation. So, to keep rainwater from running off building and onto the soil surrounding the foundation, potentially causing the pagoda to sink, builders extended the eaves far away from the walls—constituting up to 50 percent or more of the building's total width. Builders employed a series of cantilevered beams to prop up the massive overhangs. Then, to combat the buildings' severe flammability, the eaves were then laden with heavy earthenware to prevent tinders from igniting the wooden structure underneath.

Side note: Boy are pagodas flammable. The Toji pagoda, Japan's tallest wooden structure, has burned to the ground after being struck by lightning three times since its first building in 824. Fire-by-lightning-strike is actually the primary way that pagodas are destroyed, hence the inclusion of the large metal spire on the roof that acts as a lightning rod. In fact, only two Japanese pagodas in the last 1400 years, the pair at Todai-ji temple, are known to have actually collapsed from shaking alone.

Source: Gizmodo.com