The marvel of earthquake-proof technology in Tokyo

I recently had the privilege of visiting Tokyo, a city bursting with history, culture and delicious food. The highlight for me (apart from the sushi) was the view of the glittering metropolis from the top of Tokyo Tower with the moody backdrop of a lightning storm. This got me thinking about buildings in Tokyo, and how they deal with the challenges that nature throws at them.

Japan sits on a tectonic fault line, meaning seismic activity is a daily occurrence in Tokyo. The city experiences over 2000 earthquakes annually, but is still ranked as the safest city in the world by the Economist Intelligence Unit (a globally respected research and economic forecasting organisation). This prompts the question of how it is so safe whilst often being at the forefront of natural disasters, and being situated on the infamous Pacific Ring of Fire?

The short answer is a mixture of ingenious technology, a large amount of funding and necessity, but as this is after all an engineering article, I will indulge you in the long answer.

Many revolutionary anti-earthquake engineering methods are used in Tokyo, such as pendulums or ‘tuned mass dampers’. These are used in skyscrapers like the Shinjuku Mitsui building and can be as heavy as 300 tonnes. They swing counter to the waves of the earthquakes, reducing vibrations in the buildings by up to 65% and allowing them to sway.

Another example of anti-earthquake technology can be found in Tokyo’s famous Skytree. Built in 2012 and standing at a towering 634 meters, it is an impressive showcase of modern Japanese engineering. It’s main defence against seismic activity is a 375 meter-tall reinforced concrete cylinder (or shinbashira in Japanese), which is fixed to the base of the tower with steel. However, it is not attached directly to the top of the skytree, but instead to an oil damper which allows the tower to shake independently from the pillar, and acts as a cushion so that the tower doesn’t hit the centre cylinder.

Of course with seismic activity, earthquakes are not the only problem, as the shifting tectonic plates also cause devastating tsunamis. To minimise the risk of Tokyo becoming a futuristic Atlantis, the Japanese government decided to dig the 6km long (concisely named) Metropolitan Area Outer Underground Discharge Channel. This 13 year long project channelled any potential floodwaters directly into the Edo river, ensuring the streets of Tokyo stay seawater-free.

As you can imagine, technology like this does not come cheap for the Japanese government, who reportedly fork out over $4.5 billion a year on disaster prevention. This astronomical cost becomes understandable once you discover that each tuned mass damper costs around $51 million and the anti-tsunami tunnel cost a whopping $3 billion.

The Japanese government’s willingness to spend this much can only be understood by looking at the history of natural disasters in Japan. Last year marked the 100 year anniversary of the Great Kanto earthquake, which was measured at 7.9 on the Richter scale and killed upwards of 140,000 people. A more recent example was the 1995 Great Hanshin earthquake, measuring 6.9 on the Richter scale and killing over 5000 people. It was this event that caused the Japanese government to enact huge legal change on the level of seismic protection in new buildings.

Thankfully, the closest we usually get to earthquakes in the UK is the bin lorry rumbling past at 7am, however Tokyo is a fascinating insight into the different challenges engineers face around the world when it comes to designing buildings.