A magnitude 6.0 aftershock was felt on Vanuatu on Wednesday, a day after a bigger tremor triggered a small tsunami.
The US Geological Survey says it occurred at mid afternoon at a depth of 41km, 75km west-northwest of Port Vila.
Tuesday's earthquake at 4.23pm shook buildings in the city for about 15 seconds.
Geoscience Australia says the latest quake was to be expected in the wake of such a large earthquake.
Since the start of July, at least three earthquakes measuring magnitude 6.0 or above have occurred in Vanuatu, while a 7.2 quake in May prompted a brief tsunami alert.
There were three major quakes last October.