Quake Beneath Tokyo: Utilize New Damage Estimates for Disaster Management Measures

Editorial

13:30 JST, December 22, 2025

The area of Tokyo and surrounding prefectures is one of the world’s most densely populated regions. Should a massive earthquake strike, significant social and economic disruption would be unavoidable. Strengthening disaster management measures is essential to maintain Tokyo’s function as the nation’s capital.

The government’s Central Disaster Management Council has revised its damage estimates for a massive earthquake with its focus directly beneath Tokyo for the first time in about 10 years. It projects the city center will experience shaking of intensity 6 or higher on the Japanese seismic scale, resulting in 18,000 fatalities and 400,000 houses and buildings completely collapsing or burning down.

The death toll was revised down from the previous estimate of 23,000. The main reason is the progress in replacing old houses with new structures meeting the latest earthquake resistance standards. With improved earthquake resistance, the estimated number of house collapses and fires has also decreased.

Nevertheless, the damage would be immense. It is crucial to remove flammable wooden houses from densely populated areas.

Waterfront areas around Tokyo Bay, with plenty of reclaimed land and soft ground, host most of the thermal power plants that provide the majority of the electricity supply to Tokyo and surrounding prefectures. The aging of sewerage pipes is also becoming increasingly noticeable, as seen in the road collapse that occurred in Yashio, Saitama Prefecture.

Therefore, serious damage to infrastructure such as electricity, water and sewerage systems is still anticipated. Power outages could affect 16 million households, an increase of 4 million from the previous estimate, and 14 million people could lose access to water.

In the wake of major earthquakes in the past, many people suffered a deterioration in their health or even died due to living in evacuation centers for prolonged periods or sleeping in their cars.

In an anticipated powerful earthquake with its focus directly underneath Tokyo, deaths related to the disaster could reach 16,000 to 41,000, potentially exceeding the direct death toll. The central and local governments must focus not only on securing water and food but also on improving conditions in evacuation centers.

New risk factors that had not been significantly considered must receive attention. High-rise condominium buildings are proliferating in the greater Tokyo area. If elevators stopped due to power outages or malfunctioning, many households would become isolated.

During a huge disaster, the capacity of government, police and fire departments to provide support has its limits. In urban areas, relationships between neighbors have weakened, diminishing their ability to help each other. It is crucial for condominiums and workplaces to discuss disaster response actions in advance.

With an estimated 4.8 million evacuees and 8.4 million people unable to return home, evacuation centers will likely be overwhelmed. It is vital to prepare an environment suitable for sheltering at home by taking such measures as securing furniture so it doesn’t fall down and stockpiling food.

False information often spreads rapidly on social media in the wake of major disasters. The government must strive to disseminate accurate information, including how to assist foreign tourists.

(From The Yomiuri Shimbun, Dec. 22, 2025)