A shallow 6.4-magnitude quake today struck off the Pacific nation of Tonga, the US Geological Survey said, but no tsunami warning was issued.
The quake hit 345 kilometres northeast of the capital Nuku'alofa at a depth of 10 kilometres.
The USGS PAGER (Prompt Assessment of Global Earthquakes for Response) issued a green alert level projecting a very low risk of casualties or economic losses.
The Hawaii-based Pacific Tsunami Warning Centre said there was no threat of a tsunami after the quake, which was followed by a 5.4-magnitude aftershock.
Tonga, almost 2,000 kilometres northeast of New Zealand, lies on the so-called "Ring of Fire", where continental plates collide causing frequent seismic activity.
