There were no reported abnormalities at any of the region's mothballed nuclear power plants.
Japan sits at the meeting place of four tectonic plates and experiences around 20% of the world's most powerful earthquakes every year.
On Friday a volcano in the far south of Japan erupted, spewing a huge column of ash high into the sky and forcing authorities to evacuate the island on which it sits.
The eruption caused no injuries and no damage was reported, but it served as yet another reminder of the volatile geology of the country.