The quake with a preliminary magnitude of 6.0 struck shortly after midday, and was centered off the coast of Miyagi Prefecture, and 30 miles below the seabed.

The quake shook a wide region, including Fukushima and Iwate prefectures, and there was no risk of a tsunami, the Japan Meteorological Agency said.

Tokyo Electric Power Co., the utility that runs Fukushima Dai-ichi, said no problems were reported there or at another one of its nuclear plants in Fukushima, and that there were no power outages and radiation monitors did not show any change.