A tsunami alert in Chile and Peru was again issued, but was later lifted after waves of 2.4ft (0.7 meters) hit coastal areas.
Chilean President Michelle Bachelet was among those evacuated on Thursday.
The quake is the strongest of several aftershocks following Tuesday’s tremor.
There have been no reports of damage from the latest quake.
The aftershock caused buildings to wobble and people to run into the streets in the port of Iquique, which was one of the cities hit by Tuesday night’s quake.
The latest quake was centred 23km (14 miles) south of Iquique.
The US Geological Survey said the aftershock had a depth of 20km (12 miles) and was felt across the border in southern Peru, where people in the cities of Tacna and Arequipa also fled buildings.