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SCMP’s Asia desk

As Mount Fuji looms tranquilly over Tokyo’s skyline, city officials are racing to prepare for a disaster that has not struck in more than three centuries – but could happen “at any time”.
For the first time, authorities in Japan’s capital have mapped out exactly how they would evacuate millions if the dormant volcano awakens, in an overhaul of the city’s disaster playbook.
The Tokyo Metropolitan Government’s new volcano disaster prevention plan outlines which roads will be cleared first and specifies evacuation protocols, in a departure from previous, more general guidelines.
This update, the second in just four months, was prompted by concerns within the metropolitan government that earlier versions of the “Tokyo Regional Disaster Prevention Plan Volcano Edition” lacked sufficient detail and were “too vague” to offer real reassurance or guidance, The Mainichi newspaper reported.
Mount Fuji has not erupted in over 300 years … but an eruption could happen at any time
Tokyo government official
The initial revision, published in May, drew on a report by the national Central Disaster Management Council from 2020, which modelled a worst-case scenario of persistent west-southwest winds for 15 days, depositing an estimated 120 million cubic metres (4.2 billion cubic feet) of volcanic ash over Tokyo – enough to blanket most of the city, which lies 100km (62 miles) east of Mount Fuji, under 2cm to 10cm (0.8 inches to four inches) of ash.
The total projected ashfall was about 2.5 times greater than the debris generated by the 2011 Tohoku earthquake and tsunami.
Transport disruption is a central concern. Even a 10cm accumulation of ash renders most two-wheel drive vehicles immobile, and wet ash as shallow as 3cm can pose similar problems.
To tackle this, the city government in March entered into its first formal agreement with the city’s road management association and other partners to deploy a fleet of specialist vehicles, including road sweepers and wheeled loaders, to clear ash from key arteries.

The most recent revision to the disaster plan sets out a hierarchy for ash removal, prioritising routes that connect government buildings and critical infrastructure, ensuring that emergency services and residents retain access to essential services.
Evacuation guidance is now more precise: residents are advised to remain at home if ash accumulation stays below 3cm. With ash depths between 3cm and 30cm, sheltering in place or moving to local evacuation centres is recommended.
Should ash exceed 30cm, the risk of structural collapse – especially for wooden buildings – would trigger a call to evacuate the city.
“Going forward, we’ll work out specific evacuation destinations outside the area,” a municipal government representative told The Mainichi.

Officials have been stepping up efforts to raise public awareness of the dangers posed by Japan’s 111 active volcanoes, as classified by the Meteorological Agency.
“Mount Fuji has not erupted in over 300 years since the Hoei eruption [in 1707], but an eruption could happen at any time,” an official told The Mainichi. “Ashfall poses risks to human health, so we want to encourage residents to stockpile masks and goggles.”
On August 26, the Cabinet Office released an AI-powered simulation illustrating the potential impact of a Mount Fuji eruption on Tokyo.
The video depicts widespread disruption to transport, power supplies, water infrastructure, residential buildings and daily life. “We want people to learn that a major eruption of Mount Fuji is possible and to visualise what kind of impact it could have on their daily lives,” an official who oversaw the video told The Asahi Shimbun.


The simulation features commentary from Toshitsugu Fujii, a professor emeritus of volcanology at the University of Tokyo, who supervised its creation.
In the video, Fujii warns that it is “somewhat abnormal” for Mount Fuji to have remained dormant for over three centuries, given its history of erupting roughly once every 30 years. “As an active and young volcano, an eruption is inevitable,” he cautions.
However, not all experts agree on the likelihood of the simulated scenario. Some have criticised the video for being “alarmist”.
“The simulation that is being shown would only ever happen under special conditions and this is not a high-probability event,” Kimiro Meguro, a professor of disaster mitigation engineering at the University of Tokyo, previously told This Week in Asia.


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Japan

In Japan, fears of ‘inevitable’ Mount Fuji eruption spur Tokyo to map out disaster plan

People walk around Gotemba, a city 100km southwest of Tokyo, with Mount Fuji in the background. Photo: AFP

A woman crosses a street in Fujiyoshida, around 95km outside Tokyo, with Mount Fuji in the background. Photo: AFP

Smoke and ash pours out of the Shinmoedake volcano in southwestern Japan during an eruption late last month. Photo: Kyodo

People walk around Gotemba, a city some 100km southwest of Tokyo, with Mount Fuji in the background. Photo: AFP

Japan warns public of catastrophic Mount Fuji eruption with ‘alarmist’ simulation

A screenshot of the video released by Japan’s Cabinet Office showing a simulate eruption of Mount Fuji. Photo: Japan’s Cabinet Office

A still from the video shows Mount Fuji erupting using generative AI. Photo: Japan’s Cabinet Office

Smoke billows from Shinmoedake, part of the Mount Kirishima cluster of volcanoes in southwestern Japan, on June 28. Photo: Kyodo

What happens if Mount Fuji erupts? Japan lays out ‘major disaster’ action plan

Cherry blossom trees at Lake Kawaguchiko with Mount Fuji in the background. Photo: Reuters

Hikers take pictures on the Yoshida route, a popular trail up Mount Fuji. Photo: EPA-EFE

Luxury hotel, railway plan for Japan’s Mount Fuji triggers backlash

Snow-covered Mount Fuji, Japan’s highest peak. Photo: AP

Tourists gather at the current restaurant and shopping area near Fifth Station on Mount Fuji. Photo: AFP

Tourists queue to board a bus at Mount Fuji’s Fifth Station last month. Photo: EPA-EFE

Tourists take pictures on the Yoshida route, one of the main trails to climb Mount Fuji. Photo: EPA-EFE

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The revised plan details everything from clearing key roads to stockpiling masks and goggles, as Tokyo prepares for a worst-case scenario


The revised plan details everything from clearing key roads to stockpiling masks and goggles, as Tokyo prepares for a worst-case scenario.


Volcanoes

Natural disasters

Tokyo

University of Tokyo (Japan)

In Japan, fears of ‘inevitable’ Mount Fuji eruption spur Tokyo to map out disaster plan

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}The revised plan details everything from clearing key roads to stockpiling masks and goggles, as Tokyo prepares for a worst-case scenario

The revised plan details everything from clearing key roads to stockpiling masks and goggles, as Tokyo prepares for a worst-case scenario