The quake made buildings sway hundreds of miles away in neighboring countries and the Chilean capital Santiago.

Officials said there were no reports of deaths, but at least 20 people were injured when roofs caved in and balconies crumbled on weaker, older buildings, mostly in Tocopilla, 75 miles (120 km) north of coastal mining city Antofagasta.

"One of the most affected zones could be Tocopilla where some houses in the western part of town, which are made of lighter materials, have been affected and we have some injured people," Deputy Interior Minister Felipe Harboe said on television.

Television images showed cars crushed under the concrete awning of a hotel in Antofagasta, where power and phone services were knocked out by the quake. Frightened residents stood in the streets.

"People ran out into the streets because of how prolonged the quake was. There was a lot of alarm but no material or human damage," said Police Chief Hernan Tamayo in Arequipa, a town farther north near the Peruvian border.

The United States Geological Service, or USGS, said the quake, 36.7 miles (60 km) deep, was centered 66 miles (106 km) west of the town of Calama and struck at 12:40 p.m. local time (1040 EST/1540 GMT).

The quake was initially reported at 7.8 magnitude by the US agency and later verified at 7.7.

Just two hours later, a second quake of 5.7 magnitude struck. The USGS said this quake, 25.5 miles (41 km) deep, was centered 36 miles (58 km) northwest of Antofagasta and struck at 1744 GMT.

The second quake was initially reported at 6.0 magnitude by the agency and later verified at 5.7.

MINES LOSE POWER

The quakes hit an area of many large copper mines. Chile is the biggest copper producer in the world, providing more than a third of annual supplies of the red metal.

BHP Billiton said work was paralyzed after power was cut off at its Escondida, Spence and Cerro Colorado copper mines.

Freeport-McMoRan Copper & Gold said operations were halted then resumed at its Candelaria mine in Chile, due to power outages, but its El Abra mine was still down without power.

Chilean state copper miner Codelco said it resumed operations at its largest division, Codelco Norte, two hours after the quake left it temporarily without power.

Big mines in the south of Peru, also a major global metals producer, said operations were not impacted.

Chilean authorities discounted the chances of a tsunami along its Pacific coast after the quake and earlier tsunami warnings elsewhere in the Pacific were lifted.

The earthquake was felt in Peru and Bolivia, Chile's neighbors to the north, and in Santiago, 870 miles (1,400 km) south of the epicenter.

Chile, like other countries around the Pacific Rim's "ring of fire" earthquake zone, has a long history of strong quakes, including the strongest recorded in recent history -- the 1960 9.5 magnitude Valdivia quake that killed thousands of people.