A strong earthquake measuring 6.1 on the Richter scale struck off northeast Japan early on Thursday, the US Geological Survey said, but no tsunami warning was issued.
The undersea quake struck at 5:57 local time at a depth of just 11.2 kilometres, 190 kilometres east of Morioka on Honshu island, it said.
On March 11, a massive magnitude 9.0 earthquake and subsequent tsunami devastated northeast region of the country, leaving more than 13,000 people dead and over 15,000 missing.
Since then, a number of strong aftershocks have hit the country.
