Use projections to reduce damage caused by massive future quakes

Editorial

13:02 JST, December 24, 2021

The damage caused by massive earthquakes or tsunami can occur anywhere in Japan. Each local government and community needs to consider how to minimize the damage on its own.

The government’s Central Disaster Management Council has drawn up damage estimates for potential massive earthquakes in the Chishima and Japan trenches that extend from Hokkaido to Iwate Prefecture.

In the worst-case scenario of a late-night quake in winter, up to 199,000 people could die if a quake takes place in the Japan Trench, while one in the Chishima Trench could result in up to 100,000 deaths.

It has been estimated that up to 320,000 people could die in a huge quake predicted to occur along the Nankai Trough, which stretches beneath the Pacific Ocean from Shizuoka Prefecture to off the coast of Kyushu, a long-feared national disaster. The combined death toll estimates for the newly projected quakes in the two trenches almost matches the figure of the Nankai Trough earthquake.

In the latest projections, most of the deaths would be caused by tsunami. If a magnitude-9 or greater quake strikes, the coastal areas would be hit by huge tsunami. It is estimated that the waves would reach as high as about 28 meters in the town of Erimo, Hokkaido, and about 30 meters in Miyako, Iwate Prefecture, along the Sanriku coast, surpassing even the tsunami generated by the 2011 Great East Japan Earthquake.

When snow accumulates on roofs in winter, buildings become more likely to collapse. Accumulated snow or icy road surfaces make it difficult to evacuate. It is not hard to imagine the death toll swelling under bad conditions.

However, there is no need to be pessimistic and hopeless. The damage estimates are only one trial calculation, and the actual number of victims in the event of an earthquake depends largely on the precautions taken.

In the plains of Honshu and Shikoku, measures have been taken widely, such as designating sturdy buildings as evacuation sites and constructing high-rise buildings specially designed for evacuation to protect people from tsunami, in preparation for tsunami from the Nankai Trough earthquake.

In addition to these measures, by promoting awareness-raising efforts among residents, such as the need to run away immediately after shaking, the death toll could be reduced by 80% in both earthquakes, according to the council.

This time, problems peculiar to cold regions were also pointed out. If a person is swallowed by a tsunami, the risk of dying from cold increases even if they survive the immersion. It was projected that up to 42,000 people would develop hypothermia.

To prevent people from being left cold and wet overnight without any help, it will be important to provide cold protection equipment at evacuation sites and to secure evacuation facilities where people can warm up. Evacuation drills in winter and at night might also be effective.

Massive earthquakes in the Chishima and Japan trenches are thought to occur every 300 to 400 years, and experts warn that “both of them are imminent.”

One of the lessons learned from the Great East Japan Earthquake was to “expect the unexpected.” It is vital for local governments, businesses and households to utilize that lesson to reduce future damage step by step, while calmly taking in the damage estimates.

— The original Japanese article appeared in The Yomiuri Shimbun on Dec. 24, 2021.