Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

154 PATA Days 2024 M E T H O D S A Digital Elevation Model (DEM; 1 m2 spatial resolution, 20 cm vertical precision), was obtained from LiDAR data from the entire Andean piedmont in the Metropolitan region (Valderas, 2020). The fault trace has been determined from the study of fault scarps and other geomorphological distinctive features like bulging and drainage systems (Fig. 2; Valderas, 2020; Campillay, 2022). This allowed the reassessment of sites previously known, together with the ongoing paleoseismological analysis of new trenches in sites found from the study of the LiDAR data (Fig. 2; Easton et al., 2022; Campillay et al., in prep.). In addition, we performed geophysical exploration of the fault at subsurface, through electrical resistivity tomography (ERT), following Díaz et al. (2014). R E S U LT S The localization of the San Ramón fault trace was assessed from direct observation of the fault from trenches and outcrops, fault scarps and other geomorphological features, and from indirect observation from subsurface geophysical exploration (Fig. 2a). It covers about 47 km long of linear distance between the northern and southern extremes, crossing the Mapocho, Maipo and Clarillo rivers (Figs. 1, 2). The fault trace exhibits a complex geometry with a general N-S orientation, with fault branches in the order of 5-10 km long oriented NNE or NNW. Direct and indirect observations of the main or secondary faults have been performed from several sites along the fault trace (Fig. 2b-f). In Peñalolén area (Fig. 2e; site e1), the fault overthrusts alluvial sediments, with a dip of about 20ºE at the surface, as observed in paleoseismological trenches (Vargas et al., 2014; Easton et al., 2018; Iglesias, 2022). Meanwhile, at subsurface in the same site, the fault dips about 50- 55ºE, according to the results from geophysical exploration through active seismic and ERT methods (Díaz et al., 2014). Fig. 2: DEM from LiDAR data (1m2 areal resolution, 20 cm vertical precision), showing the location of the San Ramón fault trace, and sites with direct observation of the main or secondary faults of the San Ramón fault system.