A magnitude 6.4 earthquake has occurred off Japan's coast, the US Geological Survey reports. The quake hit at around early morning today, about 149 kilometers southeast of the city of Katsuura in the southern Chiba Prefecture. <br/><br/>The epicenter was located at a depth of 10 kilometers. There were no immediate reports of damages or casualties. According to the Japan Meteorological Agency, minor tremors were felt in nine different prefectures.