"Naturally" is probably not the best term, but I wonder if one chose a random city and poked about with a Geiger Counter, would one find similar figures to those reported here by a civic group and relayed by the South China Morning Post:
The tests were also carried out at the planned site of the Olympic Village and the media centre, with the highest radiation reading - 0.484 microsieverts per hour - detected in undergrowth close to Yumenoshima Stadium, where the equestrian events will be held.
However, an organisation (that I consider to be trustworthy) who monitor levels across Tokyo and the North-East said this:
"It is difficult to have this debate unless we know for sure whether this radiation is from Fukushima or whether it is naturally occurring background radiation," said Pieter Franken, founder of the Japan office of the environmental monitoring organisation Safecast.
Furthermore, the civic group also said:
"We found caesium-137 at almost every place we carried out tests, and there was no caesium here before the accident at Fukushima,"
This would be untrue, I would say, as fallout from South Pacific nuclear tests would have produced caesium-137.