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Mount Fuji Eruption Imminent? 2011 Quake Building Pressure

Volcanologists speculate that a disaster is imminent

- Common Dreams staff

Japan's Mount Fuji (Flickr/emrank)

Disaster in the making? Mount Fuji pierces the clouds on August 4, 2012. (Chunichi Shimbun/Japan Times) Scientists say last year's Great East Japan Earthquake has greatly increased the pressure of the magma chamber underneath Mount Fuji. The pressure is now higher than it was the last time the volcano erupted more than 300 years ago, scientists say, according to a report Thursday.

Mount Fuji, in Shizuoka Prefecture, last erupted in 1707, less than two months after a large earthquake.

That blast scattered ash and cinders as far as Tokyo, 60 miles from the volcano.

Last year's earthquake and Fukushima nuclear crisis were unparalleled disasters, but people in and around Shizuoka Prefecture fear the ultimate catastrophe — the eruption of Mount Fuji — may be looming.

Experts at Japan's National Research Institute for Earth Science and Disaster Prevention say there is heightened pressure under Mount Fuji due to last year's devastating earthquake and aftershocks. It is feared the increase in pressure could trigger an eruption.

When Mount Fuji last erupted, the pressure caused by the prior earthquake was weaker than that of last year, the researchers said.

In May a team of researchers warned that the mountain may collapse if a newly-discovered fault-line underneath it shifts.

Based on the tectonic movements caused by the magnitude 9.0 quake that struck March 2011 and the magnitude 6.4 quake that followed four days later, the researchers estimate that about 1.6 megapascals of pressure were placed on the magma chamber, which is thought to be some 15 km underground. That's equivalent to an atmospheric pressure of some 15.8 kg per sq. cm.

In the past, 0.1 to several megapascals of pressure have been enough to trigger volcanic eruptions, including at Mount Fuji, it said. Although conditions in the magma chamber vary, 1.6 megapascals is "not a small figure," said Eisuke Fujita, a senior researcher at the institute.

A 2004 Japanese government report estimated that an eruption would cost the country over $30 billion US dollars. A new study is focusing on the potential damage that would be caused by a series of simultaneous earthquakes along the Nankai Trough, where it is feared another earthquake will soon take place. The most recent models have revealed that, in the worst-case scenario, 323,000 people would die and the tremors could trigger an eruption at Mount Fuji.

The huge quake of March 11, 2011 and tsunami that it generated devastated a large area of the country's northeast, killing around 19,000 people and generating the nuclear emergency at Fukushima.

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This one-minute exposure taken from the eighth station on Mount Fuji shows a night view of Tokyo, with Tokyo Skytree on the left and Tokyo Tower at the lower right. (Provided to Asahi Shimbun by Suguru Minamikawa)

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Tokyo with Mt. Fuji in the background. (Flickr/wili_hybrid)

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