A powerful earthquake struck Japan on Thursday, triggering a tsunami warning for one prefecture and advisories in other prefectures.

The Japan Meteorological Agency said the quake was a magnitude of 7.4. The U.S. Geological Survey said it was 7.1.

There were no reports of casualties from anywhere in the earthquake zone, the National Police Agency said.

Workers evacuated the Fukushima Daiichi nuclear plant following the quake, the Tokyo Electric Power Company said. Tokyo Electric said it has communication with the plant and the power is still on there. There were no immediate reports of damage, it said.

The quake's epicenter was off the coast of Miyagi in northeastern Japan, the Japan Meteorological Agency said.

The U.S. Geological Survey said the quake was centered 41 miles (66 kilometers) from Sendai -- one of the areas worst hit by last month's 9.0-magnitude quake -- and 73 miles (118 kilometers) from Fukushima, where a crisis has been under way at the nuclear plant since last month's tsunami.