In 2011, a magnitude-9.0 earthquake rocked the Fukushima region — the largest ever recorded to have hit Japan. Around 20,000 people were killed, and walls of water 30 feet high damaged nuclear reactors.
Following Tuesday's quake, TEPCO, the operator of the Fukushima nuclear plant, said a cooling system had stopped in one of its reactors, NHK reported. However, there was no immediate danger and it came back online 90 minutes later, the company said.