The quake hit at 1346 IST (0816 GMT) at a depth of 10 kilometres, 96 kilometres south-southeast of Ifalik in Micronesia, the United States Geological Survey (USGS) said.
It followed another 6.1-magnitude quake which hit in almost exactly the same location earlier today.
The Hawaii-based Pacific Tsunami Warning Centre said there was no threat of a destructive widespread tsunami.