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Going deep to learn secrets of Japan's earthquakes

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Staff Writer | March 7, 2017
Tohoku-Oki earthquake
Nature   Japanese researchers and their Norwegian partners

The March 11, 2011 Tohoku-Oki earthquake was the largest and most destructive in the history of Japan.

Japanese researchers and their Norwegian partners are hard at work trying to understand just what made it so devastating.

The massive earthquake that rocked Japan on 11 March 2011 killed more than 20,000 people, making it one of the most deadly natural disasters in the country's history.

Virtually all of the victims drowned in a tsunami that in places was more than 30 metres high.

The tsunami also crippled the Fukushima Daiichi nuclear power plant, causing meltdowns in three of the plant's six reactors and releasing record amounts of radiation to the ocean.

The reactors were so unstable at one point that the former Prime Minister, Naoto Kan, later admitted he considered evacuating 50 million people from the greater Tokyo region. Eventually, 160,000 people had to leave their homes because of radiation.

This national disaster, Japan's largest-ever earthquake, was a call to action for Japanese earth scientists. Their mission: to understand exactly what happened to make this quake so destructive. For this, they turned to JAMSTEC, the Japan Agency for Marine-Earth Science and Technology to probe the secrets in the 7000-metre deep Japan Trench, the epicentre of the temblor.

In the five years since the disaster, researchers have found intriguing clues as to what made the quake so dangerous.

Norwegian petroleum expertise from working on the Norwegian Continental Shelf is now helping to uncover new details as scientists continue to try to understand what factors contribute to making an earthquake in this region really big.

In doing so, they hope to be able to better predict the magnitude and location of future quakes and tsunamis.

Japan sits in what may be one of the most dangerous places possible when it comes to earthquakes. The northern part of the country lies on a piece of the North American plate, whereas the southern part of the country sits on the Eurasian plate.

In the north, the Pacific plate is sliding underneath the North American plate, while to the south, the Eurasian plate is riding over the Philippine Sea plate. When one plate moves in relation to another, the movement can trigger an earthquake and tsunami.

The complex jumble of tectonic plates explains why roughly 1,500 earthquakes rattle the country every year, and why it is home to 40 active volcanoes - 10 per cent of the world's total.

Given that Japan experiences so many earthquakes, the quake that shook the country on the afternoon of 11 March wasn't completely unexpected. In fact, researchers predicted that the region would see an earthquake of 7.5 magnitude or more over the next 30 years.

Earthquakes are routine enough in Japan that the country has strict building codes to prevent damage.

Most large buildings wriggle and sway with the shaking of the earth - one man in Tokyo told the BBC that the movements in his workplace skyscraper during the 2011 quake were so strong he felt seasick - and even the Fukushima Daiichi nuclear plant was protected by 10-metre-high seawall.

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