00:00The central pillar of a pagoda is only attached at the top level.
00:07It's independent from the lower levels.
00:10Thanks to the central pillar, any distortion resulting from an earthquake is spread evenly
00:15over the five levels, ensuring a seismic shock isn't concentrated in one spot where it could
00:21cause a rupture.
00:23But today, Tokyo is a city of skyscrapers.
00:27And this presents complex problems.
00:31In 1923, with an epicenter 30 miles south of Tokyo, the 7.9 Kanto earthquake and resulting
00:39floods and fires killed nearly 200,000 people.
00:44But Tokyo learned from the tragedy.
00:48It turns out that the few structures back then that were made out of reinforced concrete
00:51were still standing.
00:54The government began a campaign that incorporated concrete into the new buildings.
00:59Architects began their restoration of Tokyo with a singular obsession, durability during
01:05an earthquake.
01:07But with such limited real estate, the Japanese need to build up.
01:12And during an earthquake, a building's height matters.
01:15When there's an earthquake, what varies greatly is the oscillation period.
01:20In other words, the time it takes the building to shift from left to right, then back left
01:24again.
01:25The lower the building, the shorter the period.
01:29The taller the building, the longer the period.
01:32When the building oscillates, it's like waving a fishing rod.
01:37The tip of the rod moves the greatest distance.
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