The U.S. Geological Survey says a strong earthquake has struck off the coast of El Salvador. The quake, with a preliminary magnitude of 6.2, struck at around 4:40 a.m. today morning. Its depth was measured at a shallow 10 kilometers (6 miles). It was followed by at least one large aftershock. The epicenter was about 60 miles (97 kilometers) from the city of Sonsonate, and 79 miles (128 kilometers) from the capital, San Salvador. There were no immediate reports of damage.