A magnitude-6.8 quake has struck about 200km southwest of Apia, Samoa, the United States Geological Survey says.
It initially measured the depth to at 32km but has since revised it a number of times.
The Pacific Tsunami warning centre said there was no tsunami threat.
Samoa Observer has reported it was one of the longest tremors felt in Samoa for some time.
It said the quake lasted for nearly a minute and there were reports of people running out of their homes into open spaces.