Authorities say the temblor occurred before dawn today at a depth of nearly 160 kilometers (99 miles). It was located 19 miles (32 kilometers) west of the capital of Fort-de-France.
Martinique's government said the quake did not cause any reported damage.
Martinique was last struck by a powerful temblor in 2007, when a magnitude-7.4 quake centered just northwest of the island severely damaged some buildings.