TOKYO -- The last confirmed eruption of Mount Fuji was back on Dec. 16, 1707, during the Edo period -- the largest of the 10 in Japan Meteorological Agency records going back to August 781.
Five centimeters of ash was observed in the area that is now the city of Kawasaki, Kanagawa Prefecture, more than 100 km away, according to the agency .
Japan's highest mountain -- which stands 3,776 meters tall and has graced many paintings, including the world-famous works of Katsushika Hokusai -- has lain largely dormant for the last three centuries. But Japanese companies have begun preparing for an eruption and the havoc it could wreak.
Real estate developer Mitsubishi Estate has made a comprehensive plan. For roughly 20 high-rises it operates in Tokyo's Marunouchi district -- such as the Marunouchi Building, home to the likes of Deloitte Tohmatsu Consulting and Bloomberg, and the New Marunouchi Building, which houses The Carlyle Group and Morrison & Foerster -- the company has secured extra filters to keep air conditioners running and will install covers on rooftop drains to prevent clogging.
Hundreds of protective masks, goggles and protective wear will be distributed to each building. The preparation is expected to cost millions of dollars.
Mitsubishi Estate is also simulating a major disruption to the transportation network. A shutdown of mass transit could affect up to 100,000 people in the 20 buildings. The company hopes to establish an early warning system, to encourage people to go home, and is weighing how to evacuate people to its other buildings.
A modern-day eruption by Mount Fuji could blanket the greater Tokyo area volcanic ash, which consists of fragments of rock and lava and can crush homes' roofs. The ash could fall into reservoirs and disrupt water flow.
Tokio Marine Holdings will help clients prepare for X-day. The insurer will tap the expertise of subsidiary Tokio Marine dR, which has a track record in assisting companies with business continuity planning.
The only known remedy for electric grids crippled by volcanic ash is to manually clean them up. There could also be unexpected damage from earthquakes triggered by volcanic activity.
The company ran a simulation based on a 1707-level eruption and estimated the impact on the Tokyo metropolitan area.
That eruption more than 300 years ago buried Tokyo, then called Edo, in a thick layer of ash. Many starved to death as ash buried farmland.
In making the estimates, Tokio Marine also borrowed from a hazard map last updated in March by prefectures including Shizuoka, Yamanashi and Kanagawa. Mount Fuji straddles Shizuoka and Yamanashi and is adjacent to Kanagawa.
Tokio Marine will offer five tiers of service, from making damage estimates to compiling recovery plans. The initial goal is to win orders from 10 or more companies a year.
A working group of the government's Central Disaster Management Council predicted in an April 2020 report that the Tokyo metropolitan area would suffer crippled rail service, power outages and water shutdowns in the worst-case scenario. The capital's Shinjuku Ward is expected to see 10 cm of ash accumulation by the 15th day after the eruption.