A comprehensive database of active and potentially-active continental faults in Chile at 1:25,000 scale

Abstract

In seismically-active regions, mapping active and potentially-active faults is the first step to assess seismic hazards and site selection for paleoseismic studies that will estimate recurrence rates. Here, we present a comprehensive database of active and potentially-active continental faults in Chile based on existing studies and new mapping at 1:25,000 scale using geologic and geomorphic criteria and digital elevation models derived from TanDEM-X and LiDAR data. The database includes 958 fault strands grouped into 17 fault systems and classified based on activity (81 proved, 589 probable, 288 possible). The database is a contribution to the world compilation of active faults with applications among others in seismic hazard assessments, territorial planning, paleoseismology, geodynamics, landscape evolution processes, geothermal exploration, and in the study of feedbacks between continental deformation and the plate-boundary seismic cycle along subduction zones.

Marine terraces of the last interglacial period along the Pacific coast of South America (1° N–40° S)

“…The segments beneath northern and central Peru (2-15 • S) and beneath central Chile (27-33 • S) are characterized by a gentle dip of the subducting plate between 5 and 10 • at depths of ∼ 100 km (Hayes et al, 2018) (Pilger, 1981;Cahill and Isacks, 1992;Gutscher et al, 2000;Ramos and Folguera, 2009). Processes that have been inferred to be responsible for the shallowing of the subduction slab include the subduction of large buoyant ridges or plateaus (Espurt et al, 2008), as well as the combination of the trenchward motion of thick, buoyant continental lithosphere accompanied by trench retreat (Sobolev and Babeyko, 2005;Manea et al, 2012). Volcanic activity, as well as the forearc architecture and distribution of upper-plate deformation, further emphasizes the location of flat-slab subduction segments (Jordan et al, 1983;Kay et al, 1987;Ramos and Folguera, 2009).…”

“…1) with predominantly north-south-striking normal faults, which result in the relative uplift of their western side (e.g., Mejillones fault, Salar del Carmen fault) (Naranjo, 1987;González and Carrizo, 2003;Cembrano et al, 2007). Coastal fault systems farther south are located in the Altos de Talinay area (30.5 • S; Puerto Aldea fault), near Valparaíso (33 • S; Quintay and Valparaíso faults), near the Arauco Peninsula (36-39 • S; Santa María and Lanalhue faults), and in between these areas (Topocalma, Pichilemu, Carranza, and Pelluhue faults) (Ota et al, 1995;Melnick et al, 2009Santibáñez et al, 2019;Maldonado et al, 2021) (Fig. 1).…”

“…Along the WSAC, staircase-like sequences of multiple marine terraces are preserved nearly continuously along the coast. These terraces comprise primarily wave-cut surfaces (Costa et al, 2000;Veloza et al, 2012;Maldonado et al, 2021), slab depth (Hayes et al, 2018), flat-slab subduction segments, active volcanos (Venzke, 2013), bathymetric features of the subducting plate, trench-sediment thickness (Bangs and Cande, 1997), segments of subduction erosion and accretion (Clift and Vannucchi, 2004), plate age (Müller et al, 2008), convergence vectors (DeMets et al, 2010), and marine terrace ages used for lateral correlation. DGM: Dolores-Guayaquil megashear; AFS: Atacama fault system; LOFZ: Liquiñe-Ofqui fault zone; FZ: fracture zone; 1: Punta Galera; 2: Manta Pen.…”

“…To evaluate the potential correlations between tectonic parameters and marine terraces, we analyzed the latitudinal variability of these parameters projected along a curved "simple profile" and a 300 km wide "swath profile" following the trace of the trench. We used simple profiles for visualizing 2D data sets; for instance, to compare crustal faults along the forearc area of the margin (Veloza et al, 2012;Maldonado et al, 2021), we projected the seaward tip of each fault. For the trench-sediment thickness, we projected discrete thickness estimates based on measurements from seismic reflection profiles of Bangs and Cande (1997), Collot et al (2002), Huene et al (1996), and Schweller et al (1981.…”

“…We projected these parameters, elevations, and uplift rates with respect to a south-north-oriented polyline that represents the trench. (a) Terrace-elevation measurements and the most important crustal faults (Veloza et al, 2012;Maldonado et al, 2021). This shows the range of altitudes in different regions along the coast and possible relationships between terrace elevation and crustal faulting.…”