The Atacama Fault is a major fault system running more than 1,000 kilometres through the arid Coastal Cordillera of northern Chile, roughly parallel to the Pacific coast. It sits in the upper plate above the zone where the Nazca Plate subducts beneath South America, and it is one of the best-exposed forearc faults in the world thanks to the hyper-dry desert.
The system began as a left-lateral strike-slip fault linked to oblique subduction during the Mesozoic, and it has since reactivated with a strong component of normal, extensional faulting. Its scarps, fault gouge and mineral veins are so well preserved in the Atacama that geologists use it as a natural laboratory for studying how faults work.
While the giant earthquakes of the region come from the offshore subduction megathrust, the Atacama Fault itself can generate shallow crustal earthquakes close to coastal cities such as Antofagasta and Taltal. Its long scarps record repeated movement, and shallow shocks near the surface can shake settlements built along the fault trace.