Chile's state copper miner Codelco said workers at its Ventanas operations, which house a smelter and refinery, had been evacuated.
"We have no problems in any divisions. There is no damage to infrastructure or personnel," Codelco said in a message on Twitter.
Less than an hour after the initial earthquake, three aftershocks all greater than magnitudes 6.1 struck the region, the U.S. Geological Survey reported.
Waves triggered by a strong earthquake had begun hitting the country's coastline, emergency service said, but there were no immediate reports of damage.
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Copper prices have struggled near six-year lows in 2015, due to an expected global market surplus this year and next, and slowing demand from top consumer China.
The global copper market is seen in a small surplus of nearly 200,000 tonnes this year, according to a median of analysts polled by Reuters in July.
But global miners such as Glencore this month have announced small cutbacks as some operations become uneconomic, tightening the supply pipeline and causing some analysts to turn cautiously optimistic on the metal.