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.
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Residents of Fort McMurray were restricted to salvaging only their clothes and pets as they were evacuated.
Warm sunshine to end the working week
The polls have now closed, and the first result is expected in an hour.