The epicentre of the quake was located in the Indian Ocean, about 209 kilometres southwest of Broome, or 1,294 kilometres southwest of Darwin.
There is no tsunami threat, according to the Australian Tsunami warning Centre.
There are no immediate reports about casualties or damage caused by the earthquake.
According to the USGS, the quake was recorded at 05:39 UTC near the coast of the Western Australia state at the depth of 10 kilometers (6.2 miles).
The European-Mediterranean Seismological Centre, in turn, said that the earthquake was a little less powerful, with its magnitude standing at 6.4.
This comes a day after a 5.5 magnitude quake hit off the coast of Surigao del Sur province in southern Philippines.
Earthquakes with magnitudes above 6.0 Richter scale are considered to be strong earthquakes, which can deal damage to a moderate number of structures in populated areas. It is usually felt in up to hundreds of kilometres from the epicentre.