5.1-magnitude quake hits off Japanese islands

The undersea quake hit at a shallow depth of 9.9 kms, 77 kms west of Chichi-shima island at 8:58 pm local time, the USGS said.

Around 20 per cent of the world's most powerful earthquakes strike Japan, which sits on the "Ring of Fire" surrounding the Pacific Ocean.

Thousands gathered last week to remember more than 6,400 victims of the huge earthquake that devastated Kobe in 1995, amid warnings from geologists that Japan was overdue another major quake.