Burgeoning Tokyo Careens Toward a Quake Calamity

TOKYO —  Far beneath this modern metropolis, the powerful forces of nature are locked in a slow but deadly battle that will some day bring this great city to its knees.

Already overcrowded and growing at a staggering rate, Tokyo sits on a deep sedimentary basin that is like a bowl of jello cradled by one of the most treacherous geological formations on the planet. Bluntly put, there are few places on Earth that are geologically less suited as a site for a great city than here on the shores of Tokyo Bay.

Three of the giant slabs of the Earth’s crust grind together here in what scientists call a “triple junction.” Two of the plates sink beneath the islands of Japan and then collide again as they plunge deep into the Earth directly below Tokyo, setting the stage for catastrophic earthquakes that have destroyed the city in the past and could well do so again in the future.

Most other earthquake-prone regions, including California, only have to worry about two colliding plates.

The threat will get worse in the years ahead because more and more land is being reclaimed from Tokyo Bay to serve the needs of millions more who are flocking to a city already strangling on its own prosperity. Scientists are concerned that land reclaimed from the bay will be particularly hazardous because such soils amplify shock waves from earthquakes.

Painfully aware of its problems, Japan is moving full speed ahead in earthquake engineering research, and the country is trying to develop the world’s best earthquake warning system before the next great quake hits. But some experts believe Tokyo is already past due for a catastrophic quake, and scientists around the world are watching to see if Japan can win a race against time.

The impact of a giant quake here could be felt around the world. Tokyo is a key player in global economics, and some officials fear that a catastrophic quake here could have a devastating effect elsewhere. Frank Press, president of the U.S. National Academy of Sciences, has speculated that a great quake here would force Japan to reclaim much of its foreign investment, possibly leading to a collapse of the world economy.

Tokyo was leveled once, in 1923, when a monstrous earthquake destroyed a city that had ignored the lessons offered in 1906 from a different city by a distant bay. “If we had understood the 1906 San Francisco earthquake, the damages from the Great Kanto Earthquake which came just 17 years later could have been avoided,” says Hirokazu Iemura of Kyoto University’s Earthquake Engineering Laboratory.

Iemura, who toured the Bay Area after last October’s quake, is afraid history may repeat itself. The recent San Francisco temblor, he said, demonstrated what scientists call “non-linear” consequences of an earthquake.

That means that in some cases the earth may tremble far more than the magnitude of the quake would suggest. The Bay Area quake suggested that Tokyo too may be much more vulnerable than experts had thought.

For this and other reasons, Tokyo, most experts agree, has much to worry about.

A study last year by Japan’s National Land Agency concluded that if a great earthquake--magnitude 8 or greater--should strike Tokyo in the middle of the night it would kill about 80,000 people. If it came at lunch time, as it did in 1923, or in the evening when stoves would be lit for cooking and heating, fires would sweep through parts of the city and the death toll could reach 150,000. Many experts here think even those grim estimates are far too low.

When the great quake strikes, as everyone here knows it must, it will hit a city that is already so crowded that on a typical day it dwarfs the worst traffic jams that Los Angeles has to offer.

Despite widespread planning efforts, there will be few places for people to run, and it will be extremely difficult to reach safety even for those who know where to go. The danger will not be just from falling objects. It will be mainly from fire.

“In the 1923 earthquake, 100,000 people burned to death,” Iemura said. That is more than twice as many as were killed directly by the 7.9 temblor. And now, all these years later, Iemura and many other experts in Japan are afraid that history may repeat itself.

“We are very afraid of fire,” said Etsuzo Shima, professor emeritus at the University of Tokyo and one of Japan’s leading earthquake experts. “We have many wooden houses and the roads are very narrow, and if there is a big fire in the region, many of them will be burned.”

Nario Oyagi, a geologist-engineer with Japan’s National Research Center for Disaster Prevention, thinks Tokyo’s congested streets pose a special problem. In his worst nightmares, he sees endless streams of cars ablaze on crowded streets, forming ribbons of fire extending out to the suburbs.

Hampered by ruptured water lines, unable to move on the jammed streets, firefighters would be helpless, forced to witness a holocaust of unthinkable dimensions.

Tokyo’s Metropolitan Fire Department has estimated that fully one-third of the city could be destroyed by fire in a great quake. Japanese authorities are well aware of their peril, and have made dramatic progress in earthquake engineering. The modern buildings of Japan are among the best engineered in the world, and even many older structures are well built because earthquakes here are so much a part of life.

But no amount of planning can reduce the geological hazard that lies beneath Tokyo.

“This is a very complex place,” said Yoshimitsu Okada, who is in charge of the most ambitious effort in the world to predict an earthquake. Okada directs a research team that hopes to predict a major quake about 100 miles south of Tokyo in time to evacuate several crowded cities.

Okada knows the quake will come some day because the geological formations beneath Japan are constantly active.

The Earth’s crust is made up of giant tectonic plates that drift around the planet. The plates slide against each other in some regions, like California, causing earthquakes. In other areas, an oceanic plate slides beneath a continental plate through subduction. The latter is the process that created the active volcanoes of the Pacific Northwest.

The islands of Japan are on the Eurasia Plate, which is sliding up over two other plates, the giant Pacific Plate (which also grinds against California on its opposite side) and the Philippine Sea Plate.

The Philippine and Pacific plates are being pushed under Japan as the powerful forces crunch together, creating volcanoes as they heat the underside of the Eurasia Plate. And unfortunately for Tokyo, directly beneath the mega-city, the two oceanic plates are colliding as they sink into the Earth’s mantle.

Temblors occur as the plates are ripped apart while being forced under the Eurasia Plate, so they strike much deeper than the shallow earthquakes in California. However, they can be quite large, well above magnitude 8, so they pose a great danger to areas on the surface.

Furthermore, the strength of an earthquake here is magnified by the geological conditions that underlie nearly the entire city of Tokyo. Like Los Angeles, Tokyo and many other cities in Japan are built on sedimentary deposits that have washed down from the mountains over millions of years.

Those deposits have formed a huge sedimentary basin beneath what is now the city of Tokyo. In some cases, that basin is up to two miles thick.

When an earthquake occurs, the waves of energy flowing from the epicenter are magnified by shifting sedimentary deposits, making the ground shaking more intense.

Tokyo has an additional problem because the bedrock on which the sedimentary basin sits is shaped somewhat like a bowl. Shock waves striking the bedrock are reflected back up toward the surface, extending the life of the earthquake.

“The duration of the shaking is very long,” said Oyagi, of the National Research Center for Disaster Prevention.

Officials here know those conditions could add up to disaster for Tokyo, a belief that was reinforced by Kyoto University’s Iemura when he returned from his tour of the San Francisco Bay Area after the Oct. 17 quake. He has concluded that Japan still has much to learn from San Francisco as well as Mexico City, which was ravaged by a 7.9 earthquake in 1985 that killed about 9,500 people and caused $3 billion in damages.

Most experts here had thought that Mexico City was an “exceptional case,” Iemura said. The sprawling city is built on an ancient lake bed, and scientists believe it was particularly vulnerable to ground failure from liquefaction. That occurs when a shallow water table causes the loose sediments to assume the characteristics of a liquid during a large earthquake.

“This (liquefaction) had been thought of as very exceptional,” Iemura said.

But the Bay Area quake demonstrated that liquefaction can occur “along the coast,” as in San Francisco’s Marina District, he added.

“Mexico had been thought so exceptional there was no need to think about it,” Iemura said. “But what about San Francisco? Is that also a special case?”

Although he thinks the question needs more study, Iemura is troubled by the fact that much of Tokyo is built on areas similar to San Francisco’s Marina District.

And like San Francisco, Tokyo is extremely short of land on which to build the high rises needed to house the millions who continue to flock to this crowded city.

The answer to the land shortage, Japanese authorities have concluded, is to reclaim more land from Tokyo Bay--a prospect that deeply troubles many experts. Many of the new structures going up in Tokyo these days are built on filled land, and some people here hope someday to fill in the entire bay, making room for even more people and more buildings.

If San Francisco was not an “exceptional case,” that trend could prove disastrous, many experts believe.

Tokyo University’s Shima believes there is only one answer, and that is to reverse the flow of people into Tokyo.

One group is proposing that the capital be moved out of Tokyo, hoping that the forced move of government workers will result in a lower death toll when the quake hits. Local authorities are resisting that suggestion, but Shima insists that some people are now taking it seriously.

“We are very afraid because we are now going to build a lot of high-rise buildings in the bay area,” he said. “That will increase the population, and that’s not so good.”

The earthquake hazards facing Tokyo are not just a local problem because Japan has become a major participant--some say the dominant player--in international economics. A devastating quake here would be felt in board rooms around the world.

Experts believe insurance companies would be able to cover only a small percentage of the loss. The Japanese government has put a ceiling of around $60,000 on each private residence in a city where a humble abode costs 10 times that amount.

And Tokyo is a major nerve center in the fragile network that constitutes the global economy.

Next: Preparing for The Big One

DANGEROUS INTERSECTION

Japan ranks among the most geologically active regions in the world. Earthquakes occur chiefly in areas where giant slabs of the Earth’s crust, called tectonic plates, either grind past each other or crunch together in a process called “subduction” that forces one plate under another.

Japan, however, has to concern itself with four plates. Most of the islands are on the giant Eurasia Plate, although the North American Plate reaches up over the Arctic and down to the northern tip of the archipelago. The Pacific and the Philippine Sea plates are being forced under the Eurasia Plate, and the two subducting plates collide directly beneath Tokyo.

That dynamic process is why the region is capable of generating catastrophic earthquakes, like the temblor that destroyed Tokyo in 1923, as well as about 1,000 smaller quakes every month.