It was a drill with a sober reminder. These children in a Tokyo elementary school were taking part in an annual earthquake simulation exercise yesterday, a day before the anniversary of the March 11, 2011 earthquake and tsunami disaster that killed thousands and set off a nuclear crisis in Japan.

Six years ago today, a nine-magnitude quake struck off the country's north-eastern coast, triggering huge black waves along a vast swathe of coastline and killing nearly 20,000 people and causing widespread damage. The massive tsunami crippled the Fukushima Daiichi nuclear plant, causing radioactive material to be released over a wide area of the countryside, contaminating water, food and air.

More than 160,000 people were evacuated from nearby towns and some 10 per cent of them still live in temporary housing in Fukushima prefecture. Most, however, have settled outside their hometowns and have begun new lives.