An earthquake with a preliminary magnitude of 7.1 struck Japan's southern Kumamoto prefecture, the Japan Meteorological Agency (JMA) says.A tsunami warning for a wave measuring 1 metre was issued after the earthquake, the JMA said.The Japanese government issued emergency earthquake warnings for Kumamoto, Nagasaki, Kagoshima, Fukuoka, Saga, Oita, and Miyazaki prefectures, all on Japan's southern Kyushu island.Japan is one of the world's most earthquake-prone countries, with a tremor occurring at least every five minutes.Located along the "Ring of Fire" of volcanoes and oceanic trenches partly encircling the Pacific Basin, Japan accounts for about 20 percent of the world's earthquakes of magnitude 6.0 or more.Kyushu Electric Power said there were no reports of irregularities at its Sendai and Genkai nuclear power stations after the earthquake.Train operator JR Kyushu said that it had suspended services, including its high-speed Shinkansen trains following the quake.On April 20 this year, a tremor measuring 7.7 hit the country's north, injuring at least 10 people and shaking large buildings in Tokyo.This prompted authorities to issue a special advisory warning of an increased risk of earthquakes of magnitude 8.0 or stronger.The advisory was lifted after a week.More to come...- Reuters