Invited review paper: Neogene to Quaternary tectonics of the coastal Cordillera, northern Chile

• Published in: Tectonophysics 2010-11, Vol.495 (1), p.93-110
• Main Authors: Allmendinger, Richard W., González, Gabriel
• Format: Article
• Language: English
• Subjects: Boundaries; Chile; Coastal; Coseismic; Deformation; Faults; Interseismic; Inversions; Seismic phenomena; Structural geology; Subduction; Surface cracks; Tectonics
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2009.04.019

The extreme aridity of the northern Chilean Coastal Cordillera enables the complete preservation of permanent deformation related to the coupling between Nazca and South America. The region between Antofagasta and Arica is characterized by four types of Late Cenozoic structures: EW-striking reverse faults; ~NS-striking normal faults; sparse WNW and NNW-striking right-lateral strike–slip faults; and unimodal and bimodal populations of surface cracks. The EW reverse faults occur only between 19° and 21°40' S latitude and have been active since at least 6 Ma to present. A March 2007 earthquake demonstrates that this deformation can occur during the interseismic phase of the plate boundary seismic cycle. The NS-normal faults are most abundant near Antofagasta and Mejillones and diminish in significance northward. Several of these faults, in both the Antofagasta and the Salar Grande area, have been reactivated as reverse faults causing minor topographic inversion. We suggest that normal faults move during both interseismic and coseismic deformation and are fundamentally very weak. Surface cracks are ubiquitous throughout the region and form by both non-tectonic and tectonic mechanisms. A significant proportion forms during coseismic deformation and thus may be used to identify long-lived rupture segments on the plate boundary. Overall, forearc deformation is very slow, with permanent strain rates of 1–5 nstrain/year and fault slip rates less than 0.5 mm/year.