An earthquake with a preliminary magnitude of 5.1 rocked Japan's central Nagano prefecture at 9:13 p.m. Friday local time (1213 GMT), the Japan Meteorological Agency (JMA) said, Xinhua reported.
The temblor was centered in the northern part of Nagano prefecture, with the epicenter at a latitude of 36.9 degrees north and a longitude of 138.5 degrees east.
The quake, with "very shallow focus," logged 5 plus in some parts of Nagano prefecture and 4 in neighboring Niigata prefecture on the Japanese seismic intensity scale which peaks at 7, according to the JMA.
So far no major damage or injuries were reported, and no tsunami warning has been issued.