Living on the edge

It's not when -- but if -- the Big One is going to hit Tokyo


It’s 6 a.m. on Saturday, and Teruyuki Kato is woken at home by the beeping of his government-issued pager. The University of Tokyo professor of geophysics knows he must act fast. He calls the local police, who arrive within minutes and transport him, sirens howling, red lights whirling, to the Meteorological Agency in Otemachi.

There, he and the five other members of the national Earthquake Assessment Committee meet and, after examining seismograph data, inform the prime minister of a major temblor about to strike the city.

The brakes must be slammed on shinkansen; expressways and factories have to be shut; gas and electricity supplies must be made safe . . . and the public has to be warned.

Hours later, at the prime minister’s command, thousands of members of the Self-Defense Forces and volunteer relief workers are put into action in response to a magnitude 7.2 quake that has devastated the capital.

Firefighters struggle through the rubble of collapsed buildings, battling raging fires consuming the city in which thousands of people have already perished. Hundreds of thousands have been injured, and even more buildings have been destroyed by fire.

Amid the chaos, millions are unable to return to their homes and have to seek shelter. Some will have to dodge a downpour of debris, masonry and glass falling off cracked high-rises. If reached unscathed, evacuation areas will provide shelter until the worst is over.

By this time, however, Kato is back at home watching an afternoon baseball game on television. His wake-up call was the opening scene of a dress-rehearsal that takes place in Tokyo each Sept. 1 — the anniversary of 1923’s Great Kanto Earthquake, a 7.9 magnitude temblor that claimed more than 140,000 lives and reduced much of the capital to burned-out rubble.

Most importantly, though, the annual “Tokyo Big Rescue” disaster drill is an attempt to prepare — mentally and physically — for the day when it is performed for real. While a repeat of 1923’s quake is not anticipated for another 150-200 years, experts believe a major one could strike at any time.

But when — not if — it does, will everything go as smoothly as the Sept. 1 drills, which are built on the assumption that we will receive one day’s warning of the quake?

“I can’t say. Nobody can,” says Kato. “It’s just one scenario out of a million. The worst case is that there is no warning, and I believe that’s the most likely.” That was the case on Jan. 17, 1995, when the Kobe area was hit by a 7.2 quake that killed more than 6,000 people — the first major seismic activity in the region for 300 years.

Many experts agree that, despite advances in seismography, for practical purposes we have not advanced much further than centuries ago when people believed quakes were caused by a giant namazu (catfish) that lived underneath around Japan that occasionally ran amok, causing the earth to shake until it spent its energy.

Since the 1960s, however, the less colorful theory of plate tectonics — the constant shifting of around a dozen ocean-sized chunks of the Earth’s crust — gave rise to the hope that quakes could one day be predicted. This is good news for Japan, where around 10 percent of the world’s seismic activity occurs.

There are two plate boundaries close to Japan’s Pacific coast; one where the Philippine Sea and Eurasian plates meet, the other where the Eurasian and Pacific plates collide. It is along these boundaries that much seismic activity occurs, with the former of particular concern for about a third of Japan’s 120 million inhabitants.

Although much of these plate boundaries are tens of kilometers out to sea, at Suruga Bay off Shizuoka Prefecture, the Philippine Sea/Eurasian plate boundary makes a sharp turn inland. Here it passes directly under Shizuoka itself before making a U-turn at Mount Fuji and returning seaward via Odawara and Sagami Bay off Yokohama — epicenter of the 1923 quake.

Millions of years ago, the Philippine Sea plate drifted northward. It bumped into the Japanese mainland and has continued to advance some 5 mm per year ever since. Over time, the massive plate has slowly been forced under the even larger and harder Eurasian plate, causing enormous friction and gradually dragging the edge of the latter down with it.

“Unfortunately, rock formations on this kind of scale do not snap,” said Peter Hadfield, a Japan-based British geologist and journalist who wrote the best-selling book “Sixty Seconds That Will Change the World — The Coming Tokyo Earthquake.”

“When the pressure gets too intense, the Eurasian Plate will simply whip back up again,” says Hadfield.

This will trigger what is predicted to be a magnitude 8 quake centered below Suruga Bay that will thrust the Tokai region, including Kanagawa Prefecture, into a frenzy of shaking. It is this quake, Hadfield says, that is commonly referred to as “the Big One” — and which experts have considered to be imminent since 1976.

In that year, another theory suggesting that the Big One was looming, based on a 150-year cycle of quakes in the area, was presented by then University of Tokyo seismology researcher Katsuhiko Ishibashi. His prediction set alarm bells ringing in the government, which moved speedily to set up the Earthquake Assessment Committee and to enact a law to help at-risk areas prepare. This was followed by the deployment of hundreds of seisometers, GPS stations and other monitoring apparatus throughout the Tokai region.

“Unfortunately,” said Osamu Kamigaichi of the JMA’s Seismological and Volcanological Department, “the Tokai quake is the only one that is really considered to be predictable. Generally . . . we only have limited knowledge of the relation between precursory phenomena and a large-scale quake.”

The Tokai quake will register around 5 on the Japanese intensity scale in Tokyo, said Kato — subjecting the metropolis to its most fearsome shaking for many years. “The physical damage will not be so great, but the social shock will be huge,” said Kato. “It will be the most violent shaking most people have ever felt. It will be very frightening.”

For this quake only, we may receive some notice. But for several others that could hit the Kanto region, any warning is doubtful.

Serving as the scenario for the annual Tokyo disaster-day drills on Sept. 1 is a 7.2 magnitude chokka-gata (directly below) temblor. This, a quake right under the city, experts say, is more probable than a rerun of the 1923 quake.

“No one has a clue when a chokka-gata will strike Tokyo,” said Hadfield, adding that monitoring is almost impossible because there is too much interference noise from industry in the area.

“Besides, there are hundreds of little faults down there — you cannot distinguish one from another.”

JMA’s Kamigaichi added: “We cannot specify the source region of a chokka-gata under Tokyo . . . due to the very thick sedimentary layer covering the region. That’s a big obstacle — rather like trying to pick out a heartbeat through a very thick blanket.”

Should such a quake hit the capital, the Tokyo Metropolitan Government estimates an immediate death toll of around 7,000, with more than 300,000 injured. While the epicenter of any chokka-gata is likely to be much deeper than the Kobe quake’s 14 km, much more damage is anticipated. The metropolitan government estimates 380,000 properties will be destroyed by fire. Others expect more.

“If such a quake hit Tokyo, we should expect at least as many deaths as in the Great Hanshin Earthquake, and probably a tenfold increase in property loss,” commented Tsuneo Katayama, president of the National Research Institute of Earth Science and Disaster Prevention.

While much of Tokyo is built on what is known as the Tokyo Horizon, a solid rock mass about 30 meters below the soil, the amount of reclaimed land in the city — especially around the bay — means lengthy shaking could cause extensive damage, according to Kyoji Sassa of Kyoto University’s Disaster Prevention Research Institute.

“On reclaimed waterfront areas . . . the land is already saturated so it is extremely dangerous after a quake,” he said. “Liquefaction is a distinct possibility.”

Intense seismic shaking can cause the solid particles in soft muds, silts and other wet land to move down, while the water shoots out at great pressure. This can cause whole buildings to topple and sections of roads or railroads to be destroyed.

In his book, Hadfield cites a 1989 Tokai Bank report that put the costs of a large quake under Tokyo at around $850 billion. A more recent evaluation by the report’s author, Hadfield said, is double that. Given Japan’s already huge debts and weak economy, this could be devastating — and not only for Japan, as the knock-on effect to the global economy would also be calamitous. Katayama is a little more optimistic. “Whereas the Kobe area was not prepared for the quake . . . we know a big one will hit Tokyo. So we must be prepared both physically and mentally. That, in itself, can save lives and decrease the level of damage. We have learned a lot since Kobe, but questions remain.” One of those questions relates to the ability of structures to withstand powerful quakes. Katayama said that before the Kobe quake he believed Japan’s structures to be more than adequate. “But I soon changed my mind.”

Although requirements for making new buildings more quake-resistant were stiffened in 1981 through a revision to the Building Standards Law, some 21 million structures nationwide predate that. Of those, more than half do not meet the new requirements, including at least 1.6 million wooden buildings in Tokyo alone.

In view of this, the Land, Infrastructure and Transport Ministry’s 2002 budget request includes a subsidy for the strengthening (or rebuilding) of such homes in densely populated areas, with the central and local governments and owners each footing a third of the typical 3 million yen bill.

Robert Geller, a professor at the University of Tokyo’s department of earth and planetary physics, is in no doubt that such measures are crucial. Claiming that action to take down or strengthen old houses could have reduced the death toll in the Kobe quake “to a few hundred,” he said: “With the current poor state of the economy, we need public works projects. But rather than building useless bridges and dams why not set up a program to identify the most dangerous buildings in urban areas and subsidize, or offer cheap loans to build safer ones? That would create jobs and eliminate risk.”

Aside from weak buildings, regulations are also lacking for such things as roof-top water tanks, large neon signs and even vending machines, all of which could cause serious injuries in the event of a large quake.

As for postquake measures, the government has done its job by setting up safe havens and emergency measures. Hundreds of facilities — baseball grounds, parks and other open spaces — have been earmarked as temporary shelters, and, in the Tokyo area, 230 sites are being secured as landing areas for fire-department and Air Self-Defense Force helicopters. A further 1,854 public facilities are designated by the metropolitan government to accomodate 3.7 million people, and municipal governments have millions of portions of bread, rice, water and other foodstuffs stored.

In the event of the Big One hitting Tokyo, the newly opened Oedo Subway Line, which is very deep and designed to withstand a magnitude 8 quake, will be closed to the public and secured for use by SDF troops and relief workers.

Despite Tokyo Gov. Shintaro Ishihara’s fear of foreigners rioting in a quake’s aftermath, it is not expected that the SDF will be required to keep the peace. “We’re not anticipating riots, so we’re not anticipating a need for SDF members to perform peacekeeping duties,” said Yasuaki Kobayashi of the metropolitan government’s disaster measures division.

Of course, no one can predict if there will be widespread rioting, no one can predict how well the emergency teams will respond, no one can predict when, where or how. But, as earthquake expert Kato said confidently, “The only thing we know about an earthquake hitting the Tokyo area is, it will.”