Strong quake jolts northern Japan, felt in Tokyo

"I saw some shattered windows and broken roof tiles," acity hall worker in Miyagi prefecture told public broadcasterNHK. "There were no collapsed buildings"

No tsunami warning was issued after the quake at 8:44 a.m.(2354 GMT), but NHK reported that bullet trains in the area hadstopped running.

The focus of the tremor was 10 km (6 miles) underground inIwate and Miyagi prefectures, the Japan Meteorological Agencysaid.

A spokesman for Tokyo Electric Power Co Inc said two of thecompany's nuclear power plants in Fukushima prefecture, justsouth of Miyagi prefecture, were running as usual and therewere no disruptions from the earthquake.

The earthquake measured upper 6 on the Japanese intensityscale, which measures ground motion. It may be impossible tokeep standing in a quake with that reading, the meteorologicalagency says.

"There was a strong vertical tremor, nothing after that," amunicipal worker told NHK.

Earthquakes are common in Japan, one of the world's mostseismically active areas. The country accounts for about 20percent of the world's earthquakes of magnitude 6 or greater.

In October 2004, an earthquake with a magnitude of 6.8struck the Niigata region in northern Japan, killing 65 peopleand injuring more than 3,000.

That was the deadliest quake since a magnitude 7.3 tremorhit the city of Kobe in 1995, killing more than 6,400.

(Writing by Hugh Lawson; Editing by Rodney Joyce)