Friday's quake occurred off the east coast of Aomori prefecture, in the north of Honshu, the main Japanese island, at a depth of 20km at 11.44am local time, according to the Japan Meteorological Agency, which issued a tsunami advisory that was lifted about two hours later.
Small waves were reported in Hokkaido and Aomori prefectures, but no serious damage or injuries were reported.
The quake followed a 7.5 magnitude earthquake Monday that caused injuries, light damage and a small tsunami on Japan's Pacific coast.
At least 34 people were injured in that quake, power was knocked out temporarily in places, and tsunami waves more than 0.6m above tide levels were measured in Kuji port in Iwate prefecture.
Authorities had warned of possible aftershocks.
Officials said after Monday's quake there was also a slight increase in the risk of a megaquake, at magnitude 8 or stronger, and a possible tsunami occurring along Japan's northeastern coast from Chiba, just east of Tokyo, to the northernmost main island of Hokkaido.
The agency urged residents in the area to monitor their emergency preparedness, reminding them that the caution is not a prediction of such a strong earthquake.
The recent quakes occurred around the area where the magnitude 9.0 quake and tsunami in 2011 killed nearly 20,000 people and destroyed the Fukushima Daiichi nuclear power plant.
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