TOKYO - An earthquake with a preliminary magnitude of 6.1 shook northeastern Japan early Sunday, but it posed no threat of tsunami, the weather agency said.
The focus of the 5:21 a.m. quake was in the Pacific off Iwate Prefecture at a depth of about 40 kilometers, according to the Japan Meteorological Agency.
The quake measured lower 5 on the Japanese seismic intensity scale of 7 in parts of Aomori and Iwate prefectures.
No abnormalities were reported at the Higashidori nuclear power plant in Aomori or at the Onagawa nuclear power complex in Miyagi Prefecture, according to Tohoku Electric Power Co.
There were also no abnormalities at a nuclear fuel reprocessing plant in Rokkasho, a Pacific coastal village in Aomori Prefecture, Japan Nuclear Fuel Ltd. said.
The quake comes just days after an M7.2 earthquake struck the same region, injuring at least 10 people, disrupting bullet train services and forcing schools to close temporarily.
Thursday's early morning quake also occurred off Iwate at a depth of 44 km, measuring upper 6 on the seismic intensity scale in Hashikami, Aomori.
At the time, the agency urged the public to remain alert for earthquakes of up to the same intensity level over the next week.
Elsewhere, Friday saw an M5.6 quake jolt the central Japan prefecture of Yamanashi and nearby areas. The late-night temblor, at a depth of around 20 km, measured lower 6 on the seismic intensity scale in Fujikawaguchiko, Yamanashi.
No abnormalities were detected in the volcanic activity of Mt. Fuji, Japan's highest peak and a volcano that straddles Yamanashi and Shizuoka prefectures.
The quake-hit area is near the convergence of multiple tectonic plates, including the Philippine Sea Plate. It was the first time since 1924 for an earthquake measuring in the 6 range on the intensity scale to strike Yamanashi.
