Introduction: Tokyo Under Threat (03:24)
Tokyo is the most populous city in the world despite its history with violent earthquakes and typhoons. For centuries, builders have come up with defenses against natural disasters.
Megalopolis Plagued by Disasters (04:28)
Tokyo is the heart of an urban region that stretches 1,200 kilometers and contains 80% of Japan's population. The city lies at the junction of four tectonic plates, and experiences a dozen large earthquakes each year.
City History (03:03)
Tokyo started as the small fishing village, Edo. The city’s Buddhist temples and Edo Castle have survived for centuries thanks to innovative designs that allowed them to absorb the shock of heavy tremors.
City Destruction (02:47)
The Kanto earthquake struck Tokyo on Sept. 1, 1923; the death toll from the quake, ensuing blaze, and tsunami exceeded 200,000. Two-thirds of the city was rebuilt only to be leveled again by Allied bombing during World War II.
Reducing Flood Damage (05:03)
Rebuilding Tokyo with concrete had unintended consequences, worsening flooding during torrential downpours. The city responded by building the biggest anti-flooding system in the world; the structure lies beneath nearby Saitama.
Building Design (03:59)
Tokyo's builders must adhere to strict anti-earthquake regulations. The Tokyo Skytree was built using the same principles as 7th century Buddhist temple pagodas. Other structures are stabilized from below by earthquake isolators.
Stabilizing Skyscrapers (07:09)
Mori Tower is equipped with a shaking alleviation system, featuring 356 dampers. Most of Tokyo's large structures are equipped with sensors that allow monitoring of walls, floors, and foundations. Older towers in Shinjuku are stabilized with cross bracing.
Tohoku Earthquake (03:27)
Powerful tremors shook Japan on March 11, 2011; Mori Tower’s earthquake resistance systems withstood the shaking. Fukushima was devastated by a tsunami that killed 18,000 people and an accident at the regional nuclear power plant.
Earthquake Preparation (06:10)
The Tohoku disaster highlighted the need to prepare for a megaquake. Authorities have outlined plans that rely on an early warning system and designated shelters. A Tokyo district known for its traditional, wooden structures is especially vulnerable.
New Building Material (02:53)
If a megaquake hits Tokyo, the cost would amount to an estimated €700 billion. A French company has recently developed a new type of concrete that is more earthquake resistant.
Heat Island Effect (04:13)
Tall buildings trap the heat produced by Tokyo’s cars and factories, creating a localized greenhouse effect. Future increases in precipitation may overwhelm flood protection infrastructure. Investing in green spaces may help curb both problems.
Credits: Tokyo Under Threat (00:38)
Credits: Tokyo Under Threat
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