Every Sept. 1, Tokyo residents are reminded of the tragedy of the Great Kanto Earthquake, which claimed more than 100,000 lives that fateful day in 1923. Now designated Disaster Prevention Day, it is a time for annual quake and fire drills.
The government estimates that 11,000 people would die in the worst-case scenario — a magnitude 7.3 quake jolting Tokyo around 6 p.m. on a weekday in winter, the worst time for fires and thus the highest casualties.
Of them, 6,200 would be fatally burned in the resultant fires, and 850,000 houses and other buildings would collapse or burn down.
That compares with 6,400 casualties and 112,000 destroyed homes and buildings in the Great Hanshin Earthquake, which struck Kobe and its vicinity at 5:46 a.m. Jan. 17, 1995.
In response to the estimate, the Cabinet Office compiled a plan in April 2006 to halve the expected casualties to 5,600 in 10 years by improving the quake resistance of houses and buildings in the Tokyo metropolitan area and taking other measures.
For example, the central government now offers subsidizes and tax breaks for reinforcing houses and buildings to raise the rate of quake-resistant structures to 90 percent from the current 75 percent.
The government is also promoting construction of buildings made of concrete or other non-wood materials.
The government is moving “at least in the right direction,” said Takashi Furumura, an associate professor of seismology at the University of Tokyo.
“These changes won’t be done quickly,” he added, implying the government should not be blamed for taking 10 years, though an earthquake could strike at any time.
The most important thing is to strengthen structures, because their collapse and the subsequent fires would account for the most deaths, Furumura said, pointing out that most earthquake-related fatalities occur in the first 15 minutes.
To make houses stronger, the central government has a lot of work ahead, he said.
It has to supervise local authorities, whose quake-related policies vary, to make sure everybody in the Tokyo metropolitan area gets the same and the best service possible in line with the national standard.
It is also important to crack down on fraud, Furumura said, referring to sham construction firms that target elderly people living in old houses and scare them into signing contracts that include unnecessary and ineffective repairs.
Another change needed is lowering quake-insurance monthly premiums for houses reinforced to be quake-resistant, he added.
Skyscrapers were built relatively recently and are not made of wood, so they are safer. But they shake much more, so furniture should be stabilized and people may get motion sickness, Furumura said.
Another issue facing Tokyo is how to deal with the massive number of pedestrians who would pack streets as they try to walk home after public transportation is rendered useless.
The government wants people to stay in buildings for a while — many of them are expected to be at work at 6 p.m. on a weekday — because otherwise streets will be as packed as a rush-hour Tokyo train, or six people per sq. meter.
This crush of humanity would prevent emergency teams and evacuation sites from functioning, and many people would be without food, water, blankets and other vital goods. Also, people would face the danger of falling objects because they wouldn’t be able to move in the congestion.
The Cabinet Office will compile measures to tackle the potential congestion problem this fall, spokesman Goro Yasuda said.
In the worse case, electricity would be knocked out immediately for about 2 million households, and it would take at least six days to get the power completely back online. About 1.2 million households would be without gas, while 11 million people would lose access to running water.
Direct damage from the quake, including destroyed buildings and other infrastructure, would amount to ¥66.6 trillion. The indirect damage, such as lost business opportunities caused by disrupted transportation, would be ¥45.2 trillion. The number of evacuees would be 7 million the day after the quake, with the number declining to 4.1 million a month later.
While postquake action plans get much attention, the science of predicting the disaster has not caught up. But at least the experts have figured out the mechanism that causes earthquakes.
The most well-known cause is a collision of two plates, which act like a thin crust of the Earth that moves along with the mantle’s circulation. As the two plates push each other, they eventually and suddenly release pressure, thus shaking them.
Quakes in Japan in this category are the magnitude 7.9 Great Kanto Earthquake, the one in the Tokachi area in Hokkaido, magnitude 8.0, in September 2003, a long-expected quake in the Tokai region, and others whose epicenters are mainly located under the seabed off north and east Japan.
The second type stems from movements of faults in a single plate. This category, called Chokka-gata in Japanese, or the “right-underneath” type, typically cause much damage because the epicenter is on land.
The magnitude 7.3 Great Hanshin Quake in January 1995, the Mid Niigata Prefecture Earthquake in October 2004, magnitude 6.8, and the quake in Iwate and Miyagi prefectures on June 14, magnitude 7.2, fall under this category.
The third type is caused by an ocean plate sinking into the mantle. These occur off east and north Japan. The fourth type is a volcano-driven quake and is rarely seen in Japan.
The Kanto region sits on the intersection of three plates — the Philippines Sea plate, the North American plate and the Pacific plate.
“That makes it prone to earthquakes with so many varieties, and thus is the most interesting area for researchers,” Furumura said, adding that a Tokyo quake could be any of the first three types.