The tremor, at a depth of 72 kilometres, hit at 4.16 am local time 81 km south of the town of Panguna in Papua New Guinea.
The USGS issued a "green alert", to say there was a low likelihood of casualties and damage.
In February the remote town of Lata was hit by a devastating tsunami after an 8.0-magnitude earthquake. The tsunami left at least 10 people dead, destroyed hundreds of homes and left thousands of people homeless.
In 2007 a tsunami following an 8.0-magnitude earthquake killed at least 52 people in the Solomons and left thousands homeless.