New quake scenario for Tokyo

The government’s Central Disaster Prevention Council on Dec. 19 predicted that if an earthquake of magnitude 7.3 occurred below Ota Ward, Tokyo, on a winter evening with winds blowing 8 meters per second (28.8 km per hour), an estimated 610,000 buildings would be destroyed by tremors or fire and that up to 23,000 people would be killed. Such a quake is given a 70 percent chance of occurring within 30 years.

If a quake of magnitude 8 — similar in strength to the 1923 Great Kanto Earthquake — hit, up to 70,000 people would be killed. The chance of this quake is forecast at 0 to 2 percent within 30 years.

The predicted damage is extensive. Fires in areas crowded with wooden buildings would burn for about two days; road traffic would remain seriously congested for several weeks; operation of subway trains would be suspended for about a week and ordinary trains, for about a month; and about 50 percent of Tokyo’s central district would suffer from interrupted water and electricity services for more than a week. Evacuees would number 3 million the first day after a major quake, increasing to 7.2 million two weeks later.

Precautionary measures could reduce the predicted damage significantly. The most important thing is to minimize fires in wooden buildings. There are some 16,000 hectares of areas crowded with wooden buildings, mainly outside the JR Yamanote loop line. Measures to help renovate these buildings and make them quake- and fire-resistant should be vigorously pushed.

At present, 87 percent of Tokyo’s buildings are reportedly quake-resistant. If this rate went up to 100 percent, the forecast number of deaths and destroyed buildings would decline by about 90 percent.

Circuit-breakers that turn off electricity when tremors are detected would also contribute to less damage. The government should consider requiring power companies to expand the use of such circuit breakers and smart meters. Faster fire-fighting and search-and-rescue responses would also save more lives.

Although the government adopted a policy outline in 2005 to cope with a major earthquake in Tokyo, it has been so slow to take concrete measures. It must deal with a lot of things, including making public buildings quake-proof, providing subsidies to make private-sector buildings quake- and fire-resistant, getting lifeline operators make their facilities quake-resistant, building shelters for evacuees, and devising plans to help injured people and those who cannot go home after a major quake.

The council said that the possibility of government buildings suffering from major damage is small, but such optimism is not warranted. Damage to government computer and communications systems must be taken into account. The central government should firm up its policy outline. It and the metropolitan government must ensure that their headquarters and subordinate sections can function properly if a major quake strikes Tokyo.

Businesses need to work out plans to continue their activities in the event of a major quake. Households and companies need to have at least a week’s worth of food and water stockpiled. The government and private sector should disperse key functions to areas outside of Tokyo that are less prone to strong quakes.