TOKYO - An earthquake with a preliminary magnitude of 6.1 hit east of Tokyo on Wednesday but no tsunami warning was issued and there were no initial reports of damage or troubles at area nuclear plants, the Japan Meteorological Agency and local media said.

The earthquake, which caused substantial shaking in Ibaragi and Chiba prefectures east of Tokyo, followed just a few hours after a magnitude 6.8 quake jolted northern Japan.

A tsunami warning was issued but later lifted after the northern Japan earthquake.

Just over one year ago, the northeast coast was struck by a magnitude 9 earthquake, Japan's strongest on record, and a massive tsunami, triggering the world's worst nuclear crisis in 25 years.