A series of tremors with magnitudes ranging from 4.9 to 5.7 struck off the coast of Japan within three hours, the US Geological Survey reports. The strongest 5.7 quake hit some 249 kilometers North East from the Japanese islet of Chichijima around 3am GMT, following 5.0, 4.9 and 5.2 shocks in the same area several hours before. Another 5.1 quake, which was also preceded by several powerful shakes, hit some 98 kilometers east of the city of Nishinoomote on the island of Tanegashima. There's been no immediate reports of any damage or injuries, and no tsunami warning was issued.