TOKYO - An earthquake measuring 7.9 struck off the northeast coast of Japan on Friday, shaking buildings in the capital Tokyo, causing "many injuries", at least one fire and triggering a 10-metre (30-ft) tsunami warning, NHK television and witnesses reported.The public broadcaster showed black smoke billowing from a building in Odaiba, a Tokyo suburb, and bullet trains to the north of the country were halted.Television showed cars bobbing in water along side fishing boats. A 50 cm tsunami hit Japan's northern coast."The building shook for what seemed a long time and many people in the newsroom grabbed their helmets and some got under their desks," Reuters correspondent Linda Sieg said.