Shaking was felt as far away as Tokyo, but was focused on the region around the crippled Fukushima nuclear power plant.
A minor tsunami of only less than 8 inches in height was generated by Saturday morning’s 6.8 magnitude quake.
At least three people were injured by the quake in Fukushima, according to Japan's NHK television.
The U.S. Geological Survey said the quake struck about 80 miles east south-east of the city of Namie at 4:22 am local time.
Numerous aftershocks were recorded.