The epicenter, with a depth of 404.8 km, was initially determined to be at 29.9862 degrees north latitude and 138.8108 degrees east longtitude.
Local geological survey authorities put the earthquake at 6.9 on the Richter scale, while the China Earthquake Networks Center said it was 6.6.
A Xinhua reporter living in downtown Tokyo said she could feel buildings shake in the strong earthquake.