Japan and the United States held Tuesday a joint drill on nuclear disaster prevention at the US Navy's Yokosuka Base in Japan.
The exercise was under the assumption that radiation monitoring posts failed after a strong earthquake hit Japan's southern Kanto region.
During the drill, Japan's Ministry of Education, Culture, Sports, Science and Technology dispatched a working group to measure radiation levels and conveyed the data to the Yokosuka government.
Japanese firefighters sent injured people to hospitals and US sailors and their families were evacuated from the base to temporary shelters.
The annual drill is the 6th of a series which began in 2007.