A 5.7-magnitude aftershock was followed by a 6.2-magnitude tremor, 10 and 12 minutes, respectively, after the first 8.2-magnitude quake hit at 8:46 pm (2346 GMT) around 100 kilometres off the coast, the USGS said.
Another seven shocks between 5 and 6 magnitude were recorded in the following half hour an area spanning approximately 150 kilometres, it said.
Chilean authorities said they were evacuating all coastal areas, but reported no casualties or significant damage.
DPA