Japandispatched troops and military aircraft to survey damage from a tremorwhich disrupted transportation services in a sparsely populated area ofthe country. Hundreds of people were trapped in trains which stoppedrunning and some highways were blocked by falling boulders.
Most of those injured apparently fell or were hit by shattering glass.
The earthquake caused power blackouts in the Tohoku region.
Authorities report none of the nuclear power plants in the area were damaged and all are operating normally.
The quake awakened people are far away as the capital, Tokyo, 550 kilometers southwest of the temblor's epicenter.
JapanMeteorological Agency official Takashi Yokota say the quake measuredsix-point-eight on the Richter scale and was focused more than 100kilometers underground in a coastal area.
The seismologistsays aftershocks are a worry but because the tremor originated so deepbelow the surface, no major subsequent tremors are expected. The agencywarns the main fear is the threat of landslides because heavy rain isexpected later in the day.
Japan's government says PrimeMinister Yasuo Fukuda has established an emergency task force at hisoffice to assess the damage and assist victims.
The island nation, located where several tectonic plates meet, is one of the world's most earthquake-prone countries.