A 7.0-magnitude earthquake struck in seas off far northern Japan and far eastern Russia on Friday,but no damage was expected.
The Japan Meteorological Agency said sea changes were possible. No tsunami warnings have been issued.
The tremor struck around midday in the Pacific Ocean at a relatively shallow depth of 10 kilometres. The US Geological Survey measured a stronger 7.2 magnitude.
Japan and Russia both claim some of the sparsely populated islands in the remote region.
The epicenter was 58 kilometres east-northeast of Kuril’sk,Russia,and 528 kilometres northeast of Nemuro,Japan.
The nearest land is the volcanic islands of Urup,Iturup and Sumushir. Hokkaido officials said the islands were not under Japanese control.
The area is about 1,500 kilometres northeast of Tokyo.