Japanese experts warn of earthquakes that could produce 34-metre tsunamis

Report following disaster last March finds waves pose bigger threat than previously thought and could inundate Pacific coast

• Associated Press in Tokyo
• guardian.co.uk, Sunday 1 April 2012 21.03 BST
• Article history

A tsunami hits residences in Natori, Miyagi prefecture, last March after the largest earthquake in Japan's recorded history hit the country's east coast. Photograph: AP

Much of Japan's Pacific coast would be inundated by a tsunami more than 34 metres (112 feet) high if an offshore earthquake as powerful as last year's occurred, according to a government panel of experts. They report that a wave of such height could result from any tsunami unleashed by a magnitude-9.0 earthquake in the Nankai trough, which runs east of Japan's main island of Honshu to the southern island of Kyushu.

An earlier forecast in 2003 put the potential maximum height of such a tsunami at less than 20 metres (66 feet).

The revised tsunami projections, contained in a report posted on a government website, are based on research following last March's magnitude-9.0 earthquake and tsunami, which spawned a 14-metre (45-foot) wave that devastated most of Japan's northeastern coast, triggered meltdowns at a nuclear power plant and killed around 19,000 people.

The catastrophe and the ensuing crisis at the Fukushima Daiichi nuclear power plant, prompted sweeping reviews of Japan's disaster preparedness and criticism over apparent failures to take into account potential risks.

The tsunami knocked out power at the 40-year-old coastal nuclear plant, leading to the worst nuclear disaster since Chernobyl in 1986. Tens of thousands of residents have had to leave the area, and it is unclear whether some will ever be able to move back.

The Fukushima plant was designed to withstand a 6-metre (20-foot) tsunami, less than half the height of the surge that hit it on 11 March, 2011.

The latest forecast shows a tsunami of up to 21 metres (69 feet) could strike near the Hamaoka nuclear plant on the south-eastern coast. Its operator, Chubu Electric Power Co, is building an 18-metre (59-foot) high sea wall to counter tsunamis. The wall is due to be completed next year.

The plant was shut down in 2011 due to estimates it has a 90% chance of being hit by a magnitude 8.0 or higher quake within 30 years.