Santiago (Reuters): A strong earthquake of magnitude 6.9 struck off the west coast of Chile on Monday, rocking the capital Santiago and briefly causing alarm along the Pacific Coast but sparing the quake-prone nation of any serious damage.

The quake was centered about 85 miles (137 km) from Santiago, and some 22 miles (35 km) west of the coastal city of Valparaiso. The U.S. Geological Survey twice revised the magnitude before settling on 6.9, strength usually capable of causing severe damage.

The epicenter's shallow depth of 15.5 miles (25 km) below the sea allowed it to be felt hundreds of miles (km) away. Santiago office buildings swayed for about 30 seconds at the end of the workday.

Closer to the epicenter, residents scrambled for higher ground, remembering the lessons of the country's devastating earthquake and tsunami in 2010.

"It was short but very powerful," said Paloma Salamo, a 26-year-old nurse, who was in a clinic in Viña del Mar, just north of Valparaiso, when the quake struck.

People ran from the facility carrying children and some headed for the hills when the tsunami alarm sounded, she said, but calm was soon restored.

"So far there has been no human loss nor significant damage," President Michelle Bachelet said, praising people for evacuating in an orderly fashion in the immediate aftermath.

Officials canceled a tsunami warning that had been issued in Valparaiso. The Pacific Tsunami Warning Center reported small tsunami waves of half a foot (15 cm).

There were no reports of structural damage in Valparaiso, but cellphone networks were down in some places, a spokesman with the local government said.