The tremor struck at a depth of 70 kilometres (43 miles), off Chiba prefecture, at 10:37 pm (1337 GMT), the Japan Meteorological Agency said.
The US Geological Survey measured the jolt at 6.1.
A massive earthquake and tsunami hit northeastern Japan on March 11, leaving more than 27,000 people dead or missing as well as crippling nuclear power reactors. (*)
Editor: Kunto Wibisono
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