The US Geological Survey and the Japan Meteorological Agency said that a 6.1 magnitude earthquake hit off Hokkaido in northern Japan on Saturday night.
After the earthquake off the coast, which was strong enough to shake the cities of Kushiro and Nemuro, there was no tsunami warning.
There were no immediate reports of damage or injuries in the major Japanese media.
The USGS said the quake happened at 10:27 pm (13:27 GMT) at a depth of about 27 miles (43 km).
An expert told NHK, a public radio station, that people should be on the lookout for earthquakes for about a week.
Japan has a lot of earthquakes because it is on the “Ring of Fire” in the Pacific. This is an arc of intense seismic activity that goes through Southeast Asia and the whole Pacific basin.
The country has strict building rules to make sure buildings can stand up to strong earthquakes. They also hold regular emergency drills to be ready for a big shake.