(Adds no reports of damage, airport closure; changes dateline, previous WASHINGTON)
QUITO, Aug 12 (Reuters) - A magnitude 5.1 earthquake struck Ecuador's capital of Quito on Tuesday, the U.S. Geological Survey said, though there were no immediate reports of damage.
The city's main airport halted operations as a precautionary measure to evaluate its infrastructure following the tremor, according to the airport's official Twitter account.
An official at a national emergency service contacted by Reuters said the group had not received any reports of serious damage.
Local television and social media showed images of dust clouds that had formed outside the city as a result of shifting earth at quarries in the area.
The moderate quake was only 4.8 miles (7.7 km) deep, with its epicenter located 14 miles northeast of Quito, a city of some 1.6 million inhabitants, the USGS said.
(Reporting by Alexandra Valencia and Sandra Maler, writing by Brian Ellsworth; editing by Mohammad Zargham, G Crosse)