It sounds like a story ripped from the parody-filled pages of The Onion, but some Japanese lawmakers really do want to build a “backup city” that would take over the functions of Tokyo, including tourism, in the event of a catastrophe.

The idea was floated last month at a Tokyo luncheon, with a follow-up in The Telegraph last week. “The idea of being able to have a backup, a spare battery for the functions of the nation … isn’t this really a good idea?” Hajime Ishii, a parliamentarian representing the ruling Democratic Party of Japan, was quoted as saying.

Support for creating an urban Plan B has grown in the wake of the earthquake and tsunami that devastated Japan in March and led to the Fukushima nuclear crisis. “Preparations are already under way at various levels at various levels to find ways of mitigating possible far-reaching consequences of a much-expected earthquake striking Tokyo,” the Foreign Correspondents Club of Japan said.

The lawmakers’ plan calls for building an urban center known as IRTBBC (Integrated Resort, Tourism, Business and Backup City) or NEMIC (National Emergency Management International City) on the 1,236-acre site currently occupied by Osaka International Airport at Itami. Today, Itami is used only as a secondary hub for domestic flights, operating in the shadow of the newer Kansai airport.

The new city would take on all the functions of the capital city in the event of an emergency. It would boast office complexes, resort facilities, parks and even casinos. The city’s centerpiece would be a tower that would rank among the tallest in the world, coming in at just over 650 meters (2,133 feet). It’d be built to house 50,000 residents and accommodate a workday population of around 200,000 people from the Osaka region, The Telegraph reported.

If the plan goes forward, it would rank among history’s most ambitious backup plans. The backers haven’t calculated the cost of building the city. For now, Ishii and his fellow lawmakers — including the Democratic Party’s Banri Kaieda, Shizuka Kamei of the People’s New Party and Ichiro Aisawa of the Liberal Democrats — are merely seeking 14 million yen ($180,000) for a feasibility study.

So far, the reaction has been mixed: Osaka’s governor, Toru Hashimoto, has been quoted as saying that his region is willing to accept the capital backup role, while Tokyo Governor Shintaro Ishihara has voiced opposition. And he may not be the only one: It just seems to me that most emergency-management officials, if not most politicians, would prefer to fortify what they have rather than building a whole new complex someplace else.

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 Tokyo - Takeo Hayashida signed on with a citizens’ group to test for radiation near his son’s baseball field in Tokyo after government officials told him they had no plans to check for fallout from the devastated Fukushima Daiichi nuclear plant. Like Japan’s s central government, local officials said there was nothing to fear in the capital, 160 miles from the disaster zone.

Getty Images Japanese policemen wearing a protective suits undergo testing for possible nuclear radiation at a screening center.

Then came the test result: the level of radioactive cesium in a patch of dirt just yards from where his 11-year-old son, Koshiro, played baseball was equal to those in some contaminated areas around Chernobyl.

 The patch of ground was one of more than 20 spots in and around the nation’s capital that the citizens’ group, and the respected nuclear research center they worked with, found were contaminated with potentially harmful levels of radioactive cesium.

 It has been clear since the early days of the nuclear accident, the world’s second worst after Chernobyl, that that the vagaries of wind and rain had scattered worrisome amounts of radioactive materials in unexpected patterns far outside the evacuation zone 12 miles around the stricken plant. But reports that substantial amounts of cesium had accumulated as far away as Tokyo have raised new concerns about how far the contamination had spread, possibly settling in areas where the government has not even considered looking.

 The government’s failure to act quickly, a growing chorus of scientists say, may be exposing many more people than originally believed to potentially harmful radiation. It is also part of a pattern: Japan’s leaders have continually insisted that the fallout from Fukushima will not spread far, or pose a health threat to residents, or contaminate the food chain. And officials have repeatedly been proved wrong by independent experts and citizens’ groups that conduct testing on their own.

 “Radioactive substances are entering people’s bodies from the air, from the food. It’s everywhere,” said Kiyoshi Toda, a radiation expert at Nagasaki University’s faculty of environmental studies and a medical doctor. “But the government doesn’t even try to inform the public how much radiation they’re exposed to.”

 The reports of hot spots do not indicate how widespread contamination is in the capital; more sampling would be needed to determine that. But they raise the prospect that people living near concentrated amounts of cesium are being exposed to levels of radiation above accepted international standards meant to protect people from cancer and other illnesses.

 Japanese nuclear experts and activists have begun agitating for more comprehensive testing in Tokyo and elsewhere, and a cleanup if necessary. Robert Alvarez, a nuclear expert and a former special assistant to the United States secretary of energy, echoed those calls, saying the citizens’ groups’ measurements “raise major and unprecedented concerns about the aftermath of the Fukushima nuclear disaster.”

The government has not ignored citizens’ pleas entirely; it recently completed aerial testing in eastern Japan, including Tokyo. But several experts and activists say the tests are unlikely to be sensitive enough to be useful in finding micro hot spots such as those found by the citizens’ group.

Kaoru Noguchi, head of Tokyo’s health and safety section, however, argues that the testing already done is sufficient. Because Tokyo is so developed, she says, radioactive material was much more likely to have fallen on concrete, then washed away. She also said exposure was likely to be limited.

“Nobody stands in one spot all day,” she said. “And nobody eats dirt.”

Tokyo residents knew soon after the March 11 accident, when a tsunami knocked out the crucial cooling systems at the Fukushima plant, that they were being exposed to radioactive materials. Researchers detected a spike in radiation levels on March 15. Then as rain drizzled down on the evening of March 21, radioactive material again fell on the city.

In the following week, however, radioactivity in the air and water dropped rapidly. Most in the city put aside their jitters, some openly scornful of those — mostly foreigners — who had fled Tokyo in the early days of the disaster.

But not everyone was convinced. Some Tokyo residents bought dosimeters. The Tokyo citizens’ group, the Radiation Defense Project, which grew out of a Facebook discussion page, decided to be more proactive. In consultation with the Yokohama-based Isotope Research Institute, members collected soil samples from near their own homes and submitted them for testing.

Some of the results were shocking: the sample that Mr. Hayashida collected under shrubs near his neighborhood baseball field in the Edogawa ward measured nearly 138,000 becquerels per square meter of radioactive cesium 137, which can damage cells and lead to an increased risk of cancer.

Of the 132 areas tested, 22 were above 37,000 becquerels per square meter, the level at which zones were considered contaminated at Chernobyl.

Edwin Lyman, a physicist at the Union of Concerned Scientists in Washington, said most residents near Chernobyl were undoubtedly much worse off, surrounded by widespread contamination rather than isolated hot spots. But he said the 37,000 figure remained a good reference point for mandatory cleanup because regular exposure to such contamination could result in a dosage of more than one millisievert per year, the maximum recommended for the public by the International Commission on Radiological Protection.

The most contaminated spot in the Radiation Defense survey, near a church, was well above the level of the 1.5 million becquerels per square meter that required mandatory resettlement at Chernobyl. The level is so much higher than other results in the study that it raises the possibility of testing error, but micro hot spots are not unheard of after nuclear disasters.

Japan’s relatively tame mainstream media, which is more likely to report on government pronouncements than grass-roots movements, mainly ignored the citizens’ group’s findings.

“Everybody just wants to believe that this is Fukushima’s problem,” said Kota Kinoshita, one of the group’s leaders and a former television journalist. “But if the government is not serious about finding out, how can we trust them?”

Hideo Yamazaki, an expert in environmental analysis at Kinki University in western Japan, did his own survey of the city and said he, too, discovered high levels in the area where the baseball field is located.

“These results are highly localized, so there is no cause for panic,” he said. “Still, there are steps the government could be taking, like decontaminating the highest spots.”

Since then, there have been other suggestions that hot spots were more widespread than originally imagined.

Last month, a local government in a Tokyo ward found a pile of composted leaves at a school that measured 849 becquerels per kilogram of cesium 137, over two times Japan’s legally permissible level for compost.

And on Wednesday, civilians who tested the roof of an apartment building in the nearby city of Yokohama — farther from Fukushima than Tokyo — found high quantities of radioactive strontium. (There was also one false alarm this week when sky-high readings were reported in the Setagaya ward in Tokyo; the government later said they were probably caused by bottles of radium, once widely used to make paint.)

The government’s own aerial testing showed that although almost all of Tokyo had relatively little contamination, two areas showed elevated readings. One was in a mountainous area at the western edge of the Tokyo metropolitan region, and the other was over three wards of the city — including the one where the baseball field is situated.

The metropolitan government said it had started preparations to begin monitoring food products from the nearby mountains, but acknowledged that food had been shipped from that area for months.

Mr. Hayashida, who discovered the high level at the baseball field, said that he was not waiting any longer for government assurances. He moved his family to Okayama, about 370 miles to the southwest.

“Perhaps we could have stayed in Tokyo with no problems,” he said. “But I choose a future with no radiation fears.”

Matthew L. Wald contributed reporting from Washington, and Kantaro Suzuki from Tokyo.