I don't know where New Scientist got their 1490 number, but the IAEA report on Chernobyl (http://www-pub.iaea.org/MTCD/publications/PDF/Pub1239_web.pdf) cited by Wikipedia gives an upper tier of 1480+ kBq/m^2 of cesium-137, except that 3100 km^2 of land in Russia, Ukraine and Belarus had at least that level of contamination. If you look at the total area at 555+ kBq/m^2 of cesium-137, you get 10300 km^2 of land which had at least that level of contamination. You'd need a circle with a radius of ~57 km to contain that much land.
Since 18 March, MEXT has repeatedly found caesium levels above 550 kBq/m2 in an area some 45 kilometres wide lying 30 to 50 kilometres north-west of the plant.
The wording here is kind of weird. Why are they using a single length to describe area? Furthermore, does "repeatedly found caesium levels above 550 kBq/m^2" mean that the entire area has that level of radioactivity or that simply they measured it in a few places and got high readings? The New Scientist article then gives high peak rates like 6400 kBq/m^2 of cesium, but fail to provide a comparison with Chernobyl. And to finish it off, they move onto talking about a totally different isotope (iodine-131). Becquerels measure the number of decay events per second, so comparing becquerel readings between two different isotopes is kind of pointless -- it doesn't compare the amount of energy being released.