Could Mount Fuji be the next Japanese volcano to erupt?
The eruption of Mount Ontake has raised fears that more of Japan's 110 active volcanoes could spring into life with little or no warning, with experts admitting they simply do not know when and where the next eruption will occur.
On the list of the 47 peaks most at risk, according to the Japan Meteorological Agency, is Mount Fuji, one of the most recognisable landmarks in the Asian country.
Less then 90 miles from Tokyo, any major eruption of the 12,388-foot mountain would have a catastrophic impact on a nation still struggling to shrug off the after-effects of the March 2011 Tohoku earthquake.
And some volcano experts have told The Telegraph trouble is brewing beneath Japan's highest mountain.
In July, a team of scientists from France and Japan issued a paper in which they warned that Mount Fuji is "under great pressure" as a result of the Tohoku earthquake and at an elevated risk of erupting.
A team of researchers headed by Florent Brenguier, of the Institute of Earth Sciences in Grenoble, 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 data gathered from 800 seismic detectors throughout Japan, the scientists learned that powerful stresses caused by the tremors were directly beneath volcanoes, and in particular the peak.
"Mount Fuji, which exhibits the greatest anomaly, is probably under great pressure, although no eruption has yet followed the Tohoku-oki earthquake," the scientists said in a statement. "The 6.4-magnitude seism that occurred four days after the 2011 quake confirms the critical state of the volcano in terms of pressure."
Volcano experts point out that the last time Mount Fuji erupted was in 1707, just 49 days after the massive 8.7 magnitude Hoei earthquake.
That eruption was so violent that it altered the profile of the peak and caused burning cinders to rain down on towns at the base of the mountain, while Tokyo was blanketed in ash.
The mountain has been dormant ever since that eruption, although a study by Japan's 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.
The implications of that study are difficult to quantify, experts said.
In tandem with that report, a government study has warned that as many as 750,000 people may be forced to flee their homes if Mount Fuji does erupt on the same scale as in 1707.
The report also warned that rail and road links between Tokyo and Nagoya, Osaka and the west of Japan would almost certainly be severed by pyroclastic flows, while flights would similarly be affected by the ash emitted during the eruption.
Exports warned if a large scale erruption did occurs, Tokyo would once again be smothered in ash, buildings would collapse under the weight and infrastructure would be severely damaged by lava flows.
"We have no direct observational record about the next eruption of Mount Fuji," Shigeru Suto, a volcano expert at Japan's National Institute of Advanced Industrial Science and Technology, told The Telegraph.
"We simply do not have enough data. There are 110 active volcanoes across Japan and 47 of them are under close observation because there are fears they could erupt, but it is very difficult to get precise observations and to make accurate predictions."
That was underlined by the Mount Ontake eruption, which occurred at 11:53 on Saturday with no warnings of what was about to happen. The death toll in Japan's worst volcanic disaster in living memory stands at 48, with authorities warning that figure will inevitably climb as more bodies are found on the mountain.
And Mr Suto pointed out that of all the volcanoes in Japan, Mount Fuji is among the most at risk.
"Mount Fuji has always suffered pressure from the Pacific tectonic plate, and that has not changed," he said. "What will happen on the mountain is just impossible to predict." telegraph