Mount Fuji ‘at risk of eruption’ after 2011 earthquake

July 2014 – JAPAN - The earthquake that sparked a devastating tsunami that killed thousands in Japan in 2011 has caused pressure to build under active volcano Mount Fuji. While Japan’s highest mountain has not erupted since 1707, scientists say the build-up of pressure caused by the magnitude-9 Tohoku-Oki earthquake has left Mount Fuji in a “critical state.” The research was carried out by scientists at the Institute of Earth Sciences in Grenoble, France, with their Japanese counterparts. It used records from 800 seismic sensors that recorded data after the earthquake to map geological disturbances in fluid in the earth’s crust, caused by seismic waves. “Our work does not say that the volcano will start erupting, but it does show that it’s in a critical state,” Dr Florent Brenguier, lead author of the publication, told The Guardian. Dr Brenguier said seismic waves travelled a long way around the world several times. “Their movement makes the earth’s crust vibrate and, rather like a shock wave, this produces breaks or cracks in the rock.”

A magnitude-6.4 earthquake four days after the tsunami was followed by many smaller aftershocks, indicating Mount Fuji was under high pressure. So should Japan prepare for an imminent eruption? “We cannot establish a direct relation of cause and effect between quakes and volcanic eruptions, even if statistically the former lead to an increase in the latter,” Dr Brenguier said. “All we can say is that Mount Fuji is now in a state of pressure, which means it displays a high potential for eruption. The risk is clearly higher.” Professor of geology at the University of NSW, Martin Van Kranendonk, said the Tohoku-Oki earthquake might have started to release fluid trapped in the earth’s crust around Mount Fuji. However there was no immediate cause for concern. “There’s a lot of very intense data-gathering around major volcanoes like Mount Fuji and if it’s really going to erupt, they’ll be able to monitor that because the volcano will change shape … [and] there will be earthquake tremors as the magma starts to rise to the surface. But at the moment there’s none of those indications.” –SMH

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