Japan was hit by two shallow earthquakes in the space of just eight minutes on Sunday, one of them measuring a strong 6.2-magnitude, but there were no reports of damage and no tsunami alert.
The 6.2-magnitude quake struck at 4:20pm (0720 GMT) off Japan's northeast Pacific coast, the national meteorological agency said, followed by a tremor with a reading of 5.7 at 4:28pm.
The US Geological Survey estimated the magnitude of the first quake at 6.0.
The depth of both quakes was about 10 kilometres, the agency said.
"Sea levels may change slightly due to the (first) earthquake but there is no fear of damage resulting from it," the agency said in a statement.
A 9.0-magnitude undersea earthquake off the same coast triggered a monster tsunami on March 11 last year, leaving about 19,000 people dead or missing and crippling the Fukushima nuclear power plant.