A strong 6.1 magnitude earthquake struck off the northern Japanese island of Hokkaido today, the US Geological Survey said.
The quake hit off the west coast of the island, about 170 kilometres north of Sapporo, at a relatively deep 236 kilometres.
The Japan Meteorological Agency recorded it as a weaker 6.0 quake.
Japan sits at the meeting place of four tectonic plates and experiences around 20 percent of the world's most powerful earthquakes every year.
But rigid building codes and strict enforcement mean even powerful tremors frequently do little damage.
A 7.8 magnitude quake that struck off the coast in May last year injured a dozen people.
A massive undersea quake that hit in March 2011 sent a tsunami barrelling into Japan's northeast coast, killing more than 15,000 people and sending three reactors into meltdown at the Fukushima nuclear plant.
