By Isabel Reynolds
TOKYO (Reuters) - An earthquake with a preliminarymagnitude of 7.0 struck off the coast of Japan's northernisland of Hokkaido on Thursday, the Japanese meteorologicalagency said, but there were no immediate reports of injuries ordamage.
A tsunami warning was issued for the area after the tremorstruck at 1:21 a.m. British time (09:21 JST) but only a 10 cm(4 inch) tsunami was observed on the Japanese coast,broadcaster NHK said.
"I felt a shake from side to side," Hiroshi Sasahara, antown official at Hiro on the southeast coast of Hokkaido toldbroadcaster NHK. "Nothing fell off from bookshelves but wefound a crack running 5-6 cm (2-2.4 inches) along the wall ofthe town office."
The focus of the tremor was 20 km (12 miles) below thesurface of the earth, off the coast of Tokachi on the sparselypopulated island of Hokkaido, about 800 km (500 miles) north ofTokyo, the Japan Meteorological Agency said. It was followed byless powerful aftershocks.
The runway at Shin Chitose Airport on Hokkaido was closedfor safety checks, as were some roads, domestic media said. Tenthousand people were advised to evacuate
Hokkaido Electric Power said its Tomari nuclear plant wasoperating normally after the quake, and Nippon Oil said itsMuroran refinery was also operating as normally.
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.
(Additional reporting by Tetsushi Kajimoto and YokoNishikawa)
