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Sunday, Feb. 26, 2012

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Tempting fate: As in many of the nation's coastal towns, people in Zushi, Kanagawa Prefecture, are rethinking its tsunami-preparedness in light of the Great East Japan Earthquake. This photo was taken by the Research Group for Active Faults in the Miura Peninsula, which undertakes research into the area's quake vulnerability. PPG SHONAN-HIRATSUKA


Danger zones

March 11, 2011, showed just how deadly a major tsunami can be. So what are Japan's coastal communities doing to avert another disaster?

Staff writer

Teruo Saito has lived most of his 79 years within a couple of hundred meters of the Pacific, in an area that has been overwhelmed by massive tsunamis twice in the last 600 years.

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You have been warned: The Kanagawa, Mie, Hyogo and Tokushima prefectural governments have recently published, in final or draft form, revised tsunami-inundation maps which indicate areas that are likely to be flooded in the event of a mega-tsunami such as the one that struck Japan's northeastern coast on March 11, 2011. Below are samples from those maps indicating towns that are particularly vulnerable. Concerned readers should consult with their local government for more detailed information.

Until last year's Great East Japan Earthquake, the retired company worker had almost never considered himself to be at risk. But now he has little choice other than to think about tsunamis when he regards his house 150 meters from the beach in Zushi, Kanagawa Prefecture, some 40 km southwest of Tokyo.

Like all of us, on March 11, 2011, Saito saw the television images of the waves devastating low-lying coastal areas of the Tohoku region to the north. He's also been on the receiving end of a concerted effort by his local government to increase citizens' tsunami awareness. That started with a hazard map he received in July telling him the location of the nearest tsunami-evacuation building. He participated in a tsunami drill in October, and around the same time began noticing signs on telegraph poles indicating how many meters above sea level the land there was.

Next year, Saito is also likely to notice two other Zushi government initiatives: Arrows painted on roadways indicating the direction people should run if a tsunami warning is issued; and a revised hazard map that will declare not only his beachside neighborhood, but Zushi's entire central shopping district, an "assumed tsunami-inundation" zone.

"In the past it never occurred to me that a tsunami could come to Zushi," said the 50-year resident of this city that's home to around 60,000 people. However, its government now appears determined to never let him forget.

And it's not just Zushi. While the seismic aftershocks of last year's quake have now mostly subsided, the reverberations in coastal communities and local governments around the country are continuing unabated. The goal, as one government official put it, is to remove sōteigai (anything that is beyond the realm of assumption) surrounding tsunamis — in other words, to avoid any repetition of what happened in Tohoku last year, when a sōteigai tsunami killed more than 15,000 people.

Still, some specialists worry that recent moves by bureaucrats like those in Zushi — including erecting warning signs and expanded inundation assumption zones — are hopelessly cosmetic.

Such critics claim that when the next big tsunami hits, those kinds of measures won't save lives as much as they will save bureaucrats' reputations: "We warned you," the suits will be able to say.

That's the cynical position. But perhaps a counterargument exists: Perhaps the forgiving Japanese public wishes for no more than such "cosmetic" measures against a danger that, after all, may not materialize for many hundreds of years.

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The creation of so-called hazard maps is the responsibility of local governments, such as Zushi City, which in Japan form the third tier of bureaucracy below the national and prefectural governments.

Zushi's hazard map — the one that Saito received last July — had actually been created in 2009. In addition to locating designated evacuation sites and buildings, it included assumed tsunami-inundation zones that were calculated on the basis of the most recent major tsunami event in the city's history, which occurred in 1923.

That tsunami was a consequence of the Great Kanto Earthquake, which is of course better known for causing conflagrations in Tokyo and Yokohama that killed more than 100,000 people. The tsunami itself measured just five or so meters at Zushi, and so when it became the model for making the hazard map, only a marginal strip around the city's coastline was predicted to be damaged. Saito's house and surrounds, which are at an elevation of just three meters — but behind an elevated coastal road that will in theory block a five-meter tsunami — were declared safe.

But after last year's quake and tsunami, many concerned residents in Zushi and other coastal areas nationwide began taking an interest in tsunami that occurred many centuries earlier than those on which most current hazard maps had been based.

One common reference point for such citizens in the Zushi area was the until-then generally forgotten explanation of why there is no pavilion housing the Great Buddha in Kamakura City, unlike ones at other similar sites around the country. That's because the one in Kamakura, just a couple of kilometers west of Zushi, was destroyed in a tsunami in 1498 and never rebuilt. For a tsunami to destroy the Great Buddha's pavilion, it would have had to reach at least 800 meters inland and be well over 10 meters high.

Concerned residents of Kamakura noted the discrepancy between those figures and the hazard map currently in use there, which, like Zushi's, was drawn up on the basis of the much lower, five-meter tsunami of 1923.

"We started getting enquiries from residents all over the prefecture immediately after the March 11 quake," explained Toshiaki Kawasaki, from the River Basin and Coastal Planning Division of Kanagawa's prefectural government, which is the layer of administration above Zushi, Kamakura and other cities within the prefecture's borders.

"In May we set up a panel to review tsunami preparedness throughout the prefecture and it soon became clear that we needed to consider plans for two types of tsunami: Those that occur once every 100 years or so, and much larger ones that occur once every 500 to 1,000 years," he said.

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The prefectural government thus commissioned experts to create maps of estimated inundation zones based on the massive tsunamis that struck in 1498, 1605 and 1703. The results, published in draft form in December 2011, were maps that simulate damage caused by waves up to two and three times higher than the five-meter breakers of 1923. They make it clear beyond doubt that Saito's house — along with much of central Zushi and Kamakura — would be swept away.

Kanagawa Prefecture's draft maps will be finalized by the end of March, and then passed on to its city governments. Then, it is intended that they will be incorporated into new hazard maps after fiscal 2012 commences in April. (Officials at Zushi and Kamakura city governments confirmed they plan to do just that.)

Similar shifts are now also playing out in the central Japan prefectures of Mie and Hyogo, and in the Shikoku Island prefecture of Tokushima.

Hyogo took the most drastic steps, announcing in October last year that it would simply double the size of its assumed tsunami. It then published new estimated inundation maps that encompass large swaths of densely populated cities such as Kobe and Akashi.

Since then, Kagawa and Oita prefectures have announced they too will undertake similar reviews of their tsunami maps.


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