A tsunami warning has been issued for the Miyagi Prefecture, marked in red on the map above.
The same area was hit by a devastating earthquake and tsunami in March 2011.
That quake triggered fuel-rod meltdowns at the Fukushima nuclear plant, causing radiation leakage, contamination of food and water and mass evacuations in the world's worst nuclear crisis since Chernobyl in 1986.
More top news
Just how does the power-sharing system in Northern Ireland work, and what happens now that talks are at "the end of the road"?
Dozens of women gathered on Westminster Bridge to form a human chain in a show of solidarity with the victims of Wednesday's terror attack.
Cold with some misty cloud by dawn