A 5.3 magnitude aftershock has jolted central Japan - the same area where an earthquake killed one person and injured more than 170 others one day earlier.
Japan's Meteorological Agency said no tsunami alert was issued for the aftershock early Monday.
Meanwhile, victims of Sunday's 6.9 magnitude quake which struck in the Sea of Japan, off the northern coast of Honshu island, spent the night in shelters. The quake flattened dozens of houses and damaged hundreds more.
The worst hit was the city of Wajima in Ishikawa prefecture. Japanese authorities issued a tsunami alert but it was lifted after a 10-centimeter wave hit the shore, causing no damage.
At around the same time, two strong earthquakes shook the Pacific island nation of Vanuatu, but there were no reports of injuries or damage.
Local officials say the first quake had a magnitude of 7.3, followed 28 minutes later by a 7.1 magnitude quake centered about the same spot.