The quake struck at 6:23 p.m. local time in the middle of the sea and had a depth of 10 kilometers, the USGS said.
Several islands and countries urged people near the coastline to move inland but authorities in some places later lifted their tsunami alerts.
HOUSTON — A powerful 7.6 magnitude earthquake struck Saturday south and southwest of the Cayman Islands. It triggered tsunami advisories for parts of the Caribbean, including Puerto Rico and the U.S.