The quake rattled windows in the Honduran capital of Tegucigalpa roughly 323 miles (519 km) to the east, but no damage was immediately reported.
The US Geological Survey said the quake, initially reported as a magnitude 7.8, was centered 125 miles (202 km)northeast of Barra Patuca in Honduras and 191 miles (307 km)southwest of George Town in the Cayman Islands.
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 1 meter (3 feet) above tide level.
The quake was very shallow, at only 6.2 miles (10 km), which would have amplified its effect.
(Reporting by Sandra Maler in Washington and Daina Beth Solomon in Mexico City; Editing by Lisa Shumaker and Michael Perry)
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