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

Fig. 1: Left: Geotectonic framework of South America showing regional tectonics. Top-right: Topo ‐ bathymetric map of the inner Aysén Fjord. Digital elevation model based on 1:50,000 topographic sheets from the Chilean Army Geographic Institute (IGM). The location of the seismic profile SL ‐ 06 is shown. Segmented blue lines show fault traces and lineaments, respectively. Bottom-right: Interpreted profile showing main fault offshore segments of the LOFS transfer zone. Color coding for seismic facies in legend. Modified from Villalobos et al. (2020). This study focuses on the Patagonian Andes of southern Chile, where the Liquiñe-Ofqui Fault System (LOFS) accommodates strike-slip and normal faulting due to the oblique subduction of the Nazca Plate (Cembrano et al., 1996; Thomson et al., 2010). The Chile Triple Junction complicates the tectonics, resulting in crustal weakening and partitioned deformation (Bangs & Cande, 1997; Cembrano et al., 2002). The LOFS is the fastest-slipping crustal strike- slip fault in the region, with validated slip rates (11.6 to 24.6 mm/year) that correlate with historical seismic events, including the Mw 7.7 earthquake in 1960 (De Pascale et al., 2021). In 2007, a seismic sequence in Aysén culminated in Mw 6.1 and Mw 6.2 earthquakes, triggering over 500 mass movements, including submarine landslides (Agurto et al., 2012; Sepúlveda et al., 2010). This sequence provides a unique opportunity to study fault- seismic hazard interactions along the LOFS. This research integrates bathymetric and seismic data to investigate fault activity in Aysén Fjord, using mass wasting deposits as paleoseismic indicators (Goldfinger et al., 2013; Van Daele et al., 2013). By correlating seismic profiles with depositional rates, we establish recurrence intervals for significant seismic events and analyze seismicity migration during the 2007 sequence, proposing a model that links fault activity, paleoseismology, and mass wasting in the fjord. This model enhances understanding of fault dynamics and seismic hazards in the Patagonian Andes. Fig. 1: Left: Geotectonic framework of South America showing regional tectonics. Top-right: Topo‐bathymetric map of the inner Aysén Fjord. Digital elevation model based on 1:50,000 topographic sheets from the Chilean Army Geographic Institute (IGM). The location of the seismic profile SL‐06 is shown. Segmented blue lines show fault traces and lineaments, respectively. Bottom-right: Interpreted profile showing main fault offshore segments of the LOFS transfer zone. Color coding for seismic facies in legend. Modified from Villalobo et al. (2020).