A 6.4 magnitude earthquake struck off the coast of Japan early today, the US Geological Survey (USGS) said, but there were no immediate reports of damage.  USGS put the quake 115km southeast of Morioka on Japan’s Pacific coast, and 31km deep. The quake was rated only 4 on Japan’s seven-point seismic scale, suggesting that no significant damage was expected, and no tsunami warning was issued.