A major 7.4-magnitude quake struck southern Japan on Wednesday, the US Geological Survey said, with experts warning of the possibility of a local tsunami.The quake hit at 3:19 am local time (1719 GMT Tuesday), 153 kilometres (95 miles) east of Chichi-shima in Japan's remote Bonin island region and at a shallow depth of just 14 kilometres. There were no immediate reports of damage or injury. The Hawaii-based Pacific Tsunami Warning Center said there was no threat of a destructive widespread tsunami. But it warned in a bulletin: "Earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within 100 kilometres of the earthquake epicentre. "Authorities in the region of the epicentre should be aware of this possibility and take appropriate action." Around 20 percent of the world's most powerful earthquakes strike Japan, which sits on the "Ring of Fire" surrounding the Pacific Ocean. But high building standards, regular drills and a sophisticated tsunami warning system mean that casualties are often minimal.