A moderate 5.0-magnitude earthquake struck off the east coast of the main Japanese island of Honshu today, seismologists said, but there were no immediate reports of casualties or damage.
The quake hit at 03:07 am IST with an epicentre 44 kilometres east-northeast of the city of Mito and 142 kilometres northeast of Tokyo, the US Geological Survey said.
It centred at a depth of about 41 kilometres beneath the sea floor.
No tsunami warning was issued.
Around 20 per cent of the world's most powerful earthquakes strike Japan.