There were no immediate reports of damage or injury from the quakes. The second quake hit just off the coast of Chiba, east of Tokyo at a shallow 6 miles below the sea surface, according to the Japan Meteorological Agency.
The earlier tremor caused a small tsunami, and several towns issued evacuation advisories to residents nearest the coast.
The Pacific Tsunami Warning Center in Hawaii said there was no threat of a Pacific-wide wave.
The same northern area was heavily damaged by last year's earthquake and tsunami. The magnitude 9.0 quake and tsunami on March 11, 2011, ravaged many Japanese northern coastal towns, leaving some 19,000 people dead or missing.
The Associated Press contributed to this report.
