An earthquake of magnitude 4.5 on Richter scale jolted east coast of Japan on 6 October.
No causality or loss of property has been reported yet.
The quake struck 255 east of Ishinomaki, Honshu, at a depth of 10km, the US Geological Survey said.
The epicentre of the quake was about 300km from Fukushima, where a nuclear disaster had caused widespread destruction in 2011.
No Tsunami warning has been issued so far.