100 Years after Great Kanto Earthquake: Lessons must be used to prepare for future urban disasters

One hundred years have passed since the 1923 Great Kanto Earthquake. Although Tokyo has changed significantly, there are still many lessons to be learned from the earthquake. The hope is that these lessons will be applied to urban disaster prevention today.

The Great Kanto Earthquake was a magnitude-7.9 temblor with a focus under western Kanagawa Prefecture. Areas of the Sagami Bay coastline and the southern part of the Boso Peninsula were hit by strong tremors estimated to be equivalent to the maximum level of 7 on the present-day Japanese seismic intensity scale.

The Kanto region has a complex underground plate system and has been repeatedly hit by major earthquakes. The probability of a magnitude-7-class temblor with a focus directly under the Tokyo metropolitan area is estimated to be around 70% over the next 30 years. People must adopt the mindset that a major disaster is imminent.

Many houses were completely destroyed by violent shaking in the Great Kanto Earthquake, and the disaster was compounded by tsunamis and landslides.

Even more serious damage was caused when a large fire broke out in Tokyo, somewhat far from the epicenter of the temblor. This was the most prominent feature of the disaster.

The earthquake occurred before noon. Many homes had fire stoves and blazes spread in various locations. Due to strong winds from a passing typhoon, the fires expanded and continued to burn for nearly two full days, mainly in the capital’s Kanda and Asakusa districts.

As many as 38,000 people burned to death on the grounds of an Imperial Japanese Army clothing depot in Tokyo’s Honjo, where disaster victims sought refuge. This figure accounts for more than 30% of the total 105,000 deaths from the disaster. It is said that a tornado-like whirl of fire struck the crowds of evacuees who had assembled on the grounds with their household goods.

Tokyo still has areas with buildings crammed close together on narrow streets, in eastern areas of the capital and in Nakano and Suginami wards, among other locations. Although the earthquake and fire resistance of buildings has improved significantly, it is hard to say that the threat of a major fire has been eliminated.

Efforts must be made to steadily do away with high concentrations of wooden houses in certain areas.

The extreme population density in Tokyo has become even more conspicuous over time, making the capital vulnerable to disasters in some respects. It is estimated that a major earthquake with a focus directly under the Tokyo metropolitan area would bring the transportation system to a halt, and millions of people would find it difficult to get home.

New dangers exist that were not an issue in 1923. Many high-rise condominium buildings have been constructed on reclaimed land in the Tokyo Bay area. There would be a risk of major disruption if electricity, water and other services were cut off due to liquefaction in the event of a major earthquake.

The government should deepen discussions from a long-term perspective on measures to alleviate the overconcentration of people in the Tokyo metropolitan area.

Sept. 1 was designated as Disaster Prevention Day in 1960 to mark the disaster and the beginning of the typhoon season in Japan. The day must be utilized as an opportunity to think about what would happen if a disaster occurred suddenly and review preparedness.

(From The Yomiuri Shimbun, Sept. 1, 2023)