A major earthquake of magnitude 7.1 has struck off the west coast of Chile, rocking the capital Santiago and generating at least two significant aftershocks.

No major damage was immediately apparent, according to an assessment by Chile's emergency services. The Chilean Navy and the Pacific Tsunami Warning Centre said the quake was not expected to cause a tsunami.

Chile's state-run Codelco, one of the largest copper mining companies in the world, said its operations were unaffected.

The quake was centred 35 km west of the coastal city of Valparaiso at a shallow depth of 10 km below the seabed, the US Geological Survey said.

Chilean authorities initially ordered a preventative evacuation of the coastal area near Valparaiso, some 97 km west of Santiago, in case of a tsunami, but cancelled it shortly afterward.

Computer models from the USGS estimated that up to 16.2 million people may have felt the earthquake, including 869,000 people who could have perceived strong shaking.

"The population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist," the USGS said.

Chile is highly earthquake-prone. A devastating 8.8-magnitude quake and the tsunami it unleashed in 2010 killed more than 500 people. It was among the strongest recorded.