A radiation dosimeter indicates 0.6 microsieverts in Shibuya, Tokyo, March 15, 2011, after an earthquake and tsunami hit northern Japan. Japan faced a potential catastrophe on Tuesday after a quake-crippled nuclear power plant exploded and sent low levels of radiation floating towards Tokyo, prompting some people to flee the capital and others to stock up on essential supplies. Radiation levels in the city of Maebashi, 100 km (60 miles) north of Tokyo, and in Chiba prefecture, nearer the city, were up to 10 times normal levels, Kyodo news agency said. [Photo/Agencies]