2022 updates regarding slip rates along Patagonia's fastest slipping strike strip faults: the Magallanes Fault (MF) and Liquiñe-Ofqui fault zone (LOFZ)

Gregory P. De Pascale, Sebastian Perroud, Francisca Sandoval, Manuel Hernandez, & Mario Persico

Published September 11, 2022, SCEC Contribution #12076, 2022 SCEC Annual Meeting Poster #088

Major plate boundary strike slip fault systems in Chilean and Argentine Patagonia provide important insight to crustal tectonics. Prior to 2020, slip rates along the Liquiñe-Ofqui fault zone (LOFZ) and the Magallanes Fault System (MFS) in Chile and Argentina were unknown. Along the LOFZ, studies by De Pascale et al. 2021 and Astuidillo et al. 2021 at sites >600 km apart yield consistent Quaternary slip rates of 11.6–24.6 mm/yr and 18.8 ± 2.0 mm/yr respectively, suggesting relatively consistent fault behaviour over long spatial distances (perhaps similar to the San Andreas and associated faults in California). An unpublished airborne lidar-derived topographic dataset along the southernmost LOFZ revealed clear strike slip and vertical displacements under the rainforest near Laguna San Rafael, Chile. The displacements when combined with published Quaternary dating provide high resolution vertical ~7 ± 2 mm/yr and dextral ~14 ± 4 mm/yr slip rates. These results are higher resolution and validate the De Pascale et al. 2021 estimates (11.6–24.6 mm/yr) and provide direct insight to Late Quaternary LOFZ behaviour. Moving southwards, along the MFS, recent work by Roy et al. 2020 in Argentina and Sandoval and De Pascale (2020) in both Argentina and Chile revealed left lateral slip rates for the first time along the Scotia and South American Plate boundary. The Sandoval and De Pascale work addressed sites the Hope, Deseado, and Magallanes Fault (MF)with MF slip rates of 7.8 ± 1.1 mm/yr (Chile) and 7.8 ± 1.3 mm/yr (Argentina). The Roy et al., 2020 work focused on Argentina and obtained slip rates of 6.4 ± 0.9 mm/yr using displacements with cosmogenic dating. The clear overlap in slip rate values from these studies show self-consistency and provide important insight into fault behaviour, however discrepancies between modelled and geologic slip rates suggest that slip is being accommodated (unsurprisingly) along other faults within the MFS besides the MF. Geologic slip rates along most of these MFS faults remain uncharacterised, however through combination of drone photogrammatry and local dating provide insight along the Deseado (at least 1 mm/yr) and Hope Faults (1.7 ± 0.4 mm/yr) in the MFS. Ongoing follow-up work (MBES, SBP, UAV/SfM) are helping to map fault locations, improve slip rates estimates, and evaluate width of deformation at the surface and help provide insight into the regional seismic hazard and neotectonics along these two major systems.

Key Words
Active faults, earthquake geology, Chile, Argentina, strike slip faults

Citation
De Pascale, G. P., Perroud, S., Sandoval, F., Hernandez, M., & Persico, M. (2022, 09). 2022 updates regarding slip rates along Patagonia's fastest slipping strike strip faults: the Magallanes Fault (MF) and Liquiñe-Ofqui fault zone (LOFZ). Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology