The undersea earthquake struck at a depth of 60 kilometres (37 miles) roughly 40 kilometres from the main island of Efate, which includes the capital Port Vila, Geoscience Australia said.
Local residents said the earth shook for about 15 seconds but did not appear to have caused significant damage. "It wasn't too much," a Port Vila hotel employee told AFP, referring to the shaking. "Everything's fine."
The Pacific Tsunami Warning Center said a 23-centimetre (9.2 inch) tsunami hit Port Vila, but warned bigger waves may be seen in other areas. "Higher wave amplitudes may yet be observed along coasts near the earthquake epicentre," the centre said.
Vanuatu, which lies between Fiji and Australia and north of New Zealand, is in the "Pacific Ring of Fire" known for its seismic and volcanic activity caused by friction between moving plates in the Earth's crust.
In May, a 7.2 earthquake prompted a brief tsunami alert, and at least three earthquakes measuring 6.0 or stronger have hit the archipelago since the start of July.
The country was hit by three major quakes last October, while a giant plume of volcanic ash has disrupted domestic flights in neighbouring New Caledonia in recent months. The US Geological Survey measured Tuesday's earthquake at 7.5 and said it was 35 kilometres deep, and just 40 kilometres from Port Vila.
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