The Japan Meteorological Agency said the quake was a stronger 7.8 magnitude and may cause a slight change of sea levels around Japanese coasts.
The U.S. National Oceanic and Atmospheric Administration said a tsunami watch was issued for the state of Hawaii, while another agency, the Pacific Tsunami Warning Center, said the quake had potential to generate a destructive tsunami.
The height is equivalent to just under a foot.
The Japan Meteorological Association warned against slight tidal changes but said no warnings or even watch advisories had been issued.
The earthquake, 218 km (135 miles) south-southeast of the town of Severo, struck at a depth of 56.7 km (35 miles), the U.S. Geological Survey (USGS) said.
There were no immediate reports of damage or casualties.