The powerful quake, which was felt in the Honduran capital Tegucigalpa, struck some 36km northeast of Great Swan Island around 2:51am GMT, according to US Geological Survey.
The Pacific Tsunami Warning Center has issued multiple tsunami advisories for the shoreline of Puerto Rico and the Virgin Islands, where it said there are threats of “fluctuations and strong ocean currents that could be a hazard along coasts … beaches … in harbors … and in coastal waters.”
Waves up to one meter above tide level are also possible in Cuba, Mexico, Honduras, Belize and Jamaica, the PTWC warned, adding that earthquakes of this size are “known to generate tsunamis dangerous to shorelines near the source.”
The quake rattled windows in the Honduran capital of Tegucigalpa roughly 519 km to the east, but no damage was immediately reported.
The Pacific Tsunami Warning Center said a tsunami advisory was in effect for Puerto Rico and the U.S. Virgin Islands after the earthquake and warned of possible waves up to one metre above tide level.
The U.S. Geological Survey said the quake, initially reported as a magnitude 7.8, was centred 202 kilometres northeast of Barra Patuca in Honduras and 307 kilometres southwest of George Town in the Cayman Islands.
It was very shallow, only 10 kilometres, which would have amplified its effect.
The agency projected that the “earliest estimated time that hazardous sea level fluctuations and strong ocean currents may begin” is after 5:20am GMT (1:20am Atlantic Standard Time).