A strong earthquake struck northeast of Tokyo late Wednesday but there was no fear of a tsunami, Japan's meteorological agency said.
It put the magnitude at 6.3, while the US Geological Survey measured it at 5.9.
The quake struck at a shallow depth of 10 kilometres (6.2 miles), 18 km north-northeast of the town of Daigo.
There were no immediate reports of injuries or damage, Chief Cabinet Secretary Yoshihide Suga told reporters, adding that no abnormalities were detected at nuclear power plants in the region.
Japan sits at the junction of four tectonic plates and experiences a number of relatively violent quakes every year. But rigid building codes and strict enforcement mean even strong tremors often do little damage.
A massive undersea quake that hit in March 2011 sent a tsunami barrelling into Japan's northeast coast, leaving more than 18,000 people dead or missing, and sending three reactors into meltdown at the Fukushima nuclear plant.
In April two strong earthquakes hit southern Japan's Kumamoto prefecture followed by more than 1,700 aftershocks, leaving at least 50 dead and causing widespread damage.