A strong 6.2-magnitude earthquake hit eastern Japan Saturday, the US Geological Survey said, but there were no immediate reports of damage.
The quake, at a depth of 44 kilometres (27 miles), struck shortly after 6:42 am (2142 GMT) near the northeast coast of the main Honshu island, some 350 kilometres from Tokyo.
No tsunami warning was issued.
Japan sits at the junction of four tectonic plates and experiences a number of relatively violent quakes every year, but rigid building codes and their strict enforcement mean even strong tremors often do little damage.
A massive undersea quake however 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.