TOKYO - A powerful earthquake jolted northwestern Japan on Tuesday night, and officials warned of a tsunami up to 3.3 feet high along parts of the coast.
Japan's Meteorological Agency said the quake registered magnitude 6.8 and was located off the western coast of Yamagata about 30 miles southwest of the city of Sakata.
It said the quake was fairly shallow, about 6 miles below the sea's surface. Shallow quakes tend to cause more damage on the Earth's surface.
The agency predicted a tsunami as high as 1 yard along the coast of the northwestern prefectures of Yamagata, Niigata and Ishikawa.
Kyodo News agency said service was suspended on two bullet train lines to check for damage.
All seven reactors at the Kashiwazaki-Kariwa nuclear plant in Niigata were off line and no abnormalities were reported.
Japan is one of the most earthquake- and tsunami-prone areas in the world. On March 11, 2011, a magnitude 9.0 offshore quake hit the northeast coast, causing a tsunami that took more than 18,000 lives and triggered a nuclear disaster at the Fukushima power plant.