Upper-plate fault activity in the Coastal Forearc of northern Chile (~23°30'S): Paleoseismology, neotectonic implications and relation with the subduction cycle
The tectonic evolution of northern Chile is controlled by the convergence between the Nazca and South America plates. This convergence is responsible for elastic strain accumulation close to the interplate contact zone. The elastic deformation is almost completely released during subduction zone earthquakes. However, part of the deformation induced by the convergence is permanently transferred to the upper-plate. This is manifested by the existence of upper-plate faults, some of them accommodating extension perpendicular to the coastal margin. In this study, we focus in the superficial upper-plate fault activity of the Antofagasta Region, at 23°30'S, in the Coastal Fore-arc of the Andes. We study in detail the Mejillones Fault, located in the Mejillones Peninsula, north of Antofagasta; and the Salar del Carmen Fault, eastward Antofagasta. The first part of the manuscript deals with the influence of the Mejillones Fault in the geomorphological configuration of the northern Mejillones Peninsula. The second part shows the results relative to the paleoseismology of both faults. Finally, we discuss the relation between the activity of these upper-plate faults and the subduction seismic cycle, using models that calculate Coulomb stress changes induced by the interseismic and coseismic stages of the interplate cycle.