Mount Fuji at greater risk of eruption due to 2011 quake, scientists warn
Scientists say stresses put on the volcano bythe disaster creates a higher risk of eruption
Scientists from Japan and France have warned that the famous volcano Mount Fuji is "under great pressure" as a result of the March 2011 earthquake, and at higher risk of eruption.
The research was headed by Professor Florent Brenguier, of the Institute of Earth Sciences in Grenoble, with the assistance of researchers in Paris and Japan.
Brenguier's team monitored seismic waves produced by the magnitude-9 earthquake to produce what they describe as an ultrasound of the earth's interior.
With access to more than 70 terabytes of seismic data gathered from 800 seismic detectors throughout Japan, the scientists were able to identify that the regions where there were perturbations in the earth's crust were not where the tremors were the strongest.
That came as a surprise to the scientists, along with evidence that the strongest stresses were beneath volcanoes - and particularly the peak that is the symbol of Japan.
"Mount Fuji, which exhibits the greatest anomaly, is probably under great pressure, although no eruption has yet followed the Tohoku-oki earthquake," the scientists wrote. "The 6.4-magnitude seism that occurred four days after the 2011 quake confirms the critical state of the volcano in terms of pressure."
Experts point out that the last time Mount Fuji erupted was in 1707, just 49 days after the massive 8.7-magnitude Hoei earthquake struck.
That eruption was so violent that it changed the profile of the peak, and burning cinders fell on nearby towns.
Toyko, about 100km to the east, was blanketed in ash and lanterns were needed to light buildings in the daytime.
Ever since, the 3,776 metre peak has been slumbering.
A study by the National Research Institute for Earth Science and Disaster Prevention indicated that the pressure in the magma chamber beneath Mount Fuji could be as much as 1.6 megapascals higher than in 1707.
A recent government study warned that as many as 750,000 people might be forced to flee their homes if Fuji did erupt on the same scale as in 1707.
It also warned rail and road links from Tokyo would almost certainly be severed by flows of a liquidised mixture of hot gases and rock, while flights would be similarly affected by the ash emitted in the eruption.