There were no immediate reports of fatalities, injuries or damages from the 6.2 magnitude and 6.8 magnitude aftershocks near the Pacific coast city of Antofagasta. Many other smaller tremors have hit since the 7.7 quake yesterday.
The strong aftershocks struck as President Michelle Bachelet travelled to Antofagasta, Chile's mining capital, to visit the quake zone. She was to go to the small towns of Tocopilla and Maria Elena, where homes and large buildings collapsed.
"We have significant damages in Tocopilla and Maria Elena as well as in other smaller towns," government spokesman Ricardo Lagos said of the two hardest-hit towns, adding that at least 15,000 people were homeless.
"People here are pretty afraid. There have been so many aftershocks that start with a big noise, a humming noise, and then the ground starts moving and people start to run away," Paula Saez, an aid worker with World Vision International, said from Tocopilla, where two people were killed.
The US Geological Survey, or USGS, originally reported the first big aftershock today as magnitude 6.5, but then revised it down to 6.2. Its preliminary reading on the second aftershock was magnitude 6.8.
Yesterday's large quake cut power to some of the world's largest copper mines, forcing them to work on backup generators today.
Copper prices jumped by more than 6 per cent yesterday to $3.3040 a pound on the New York Mercantile Exchange's COMEX division. That price backed off 4.11 per cent in early trade today.