A strong earthquake has struck Vanuatu's Erromango island in the Pacific Ocean and another earthquake hit off the coast of Japan.

These follow two other earthquakes that rocked Southland, Marlborough and the lower North Island in New Zealand yesterday.

Almost exactly one hour after a 5.8 magnitude earthquake struck 585km south-west of Invercargill at 1.43pm, the Cook Strait was rattled by a 5.1 quake that struck 30km north-east of Seddon.

Vanautu's magnitude 6.4 quake struck the centre of the island, it's fourth largest, at 7.09am on Thursday (local time) and was fairly deep at 200km, which would have dampened its effect, the US Geological Survey says.

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Erromango has a population of just under 2000 people.

The Vanuatu archipelago, east of Australia in the Pacific Ocean, is in the so- called Ring of Fire and is prone to earthquakes.

Earlier today, a magnitude 6.1 earthquake has hit off the coast of Japan, the US Geological Survey says.

The agency's website says the quake hit early on Thursday about 283 kilometres southeast of the city of Kamaishi and more than 322km east of Fukushima.

A massive 2011 earthquake and tsunami caused meltdowns at three reactors in the Fukushima nuclear plant.

Fewer than 40 reports of people feeling Thursday's quake were registered on the Geological Survey website.

Mexico is reeling from a magnitude-7.1 earthquake that collapsed buildings and killed at least 225 people.