A magnitude 6.1 quake struck off Aomori in northern Japan on March 28, the national weather agency said, but no tsunami warning was issued.
The quake hit at 6:18 p.m. (09:18 GMT) at a depth of 20 kilometres (12 miles), according to the Japan Meteorological Agency.
Major Japanese media outlets carried no immediate reports of damage or injuries.
The U.S. Geological Survey put the magnitude of the quake at 6.2.
Earthquakes are common in Japan, which sits on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches through Southeast Asia and across the Pacific basin.
The country has strict construction regulations intended to ensure buildings can withstand strong earthquakes, and emergency drills are routinely held to prepare for a major jolt.
