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

388 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E PATA Days 2024 K E Y W O R D S Pampean f lat-slab, thrust faults, active tectonics, seismic hazard (1) Departamento de Geología, Universidad de Chile, Plaza Ercilla 803, 8370450 Santiago, Chile. (2) Xterrae Geología, Hernando de Aguirre #194, Oficina 61, Providencia, Santiago, Chile. (3) University of Iceland, Faculty of Earth Science and Institute of Earth Sciences, Reykjavik #102, Iceland. (4) University of Toulouse, CNRS, IRD, GET, UPS, 31400, Toulouse, France. (5) Baylor University, Department of Geology, One Bear Place #97354, Waco, Texas 76798-7354, USA. *Email: lpinto@uchile.cl Luisa Pinto (1) José Estay (2) Javiera Quezada (1) Gabriel Easton (1) Gregory de Pascale (3) Miguel Troncoso (1) Sebastien Carretier (4) Steve Forman (5) CARIÑO BOTADO FAULT SYSTEM: ACTIVE THRUST TECTONICS ALONG THE WESTERN MARGIN OF THE ANDEAN PRINCIPAL CORDILLERA (~33°S , CHILE) A B S T R A C T The Cariño Botado Fault System corresponds to a Quaternary fault developed on the western edge of the Principal Cordillera, Chilean Andes (~33°S). We conducted a stratigraphic and sedimentological study on syntectonic alluvial fans associated with the activity of this Quaternary fault system, as well as morphostructural analysis, OSL dating of alluvial sediments, and U-Pb dating of fluvial detrital zircons that allowed us to constrain the age and displacement of its tectonic activity, as well as establish its effect on landscape modeling. The most relevant conclusions are that this fault system has a trace length of ~5-15 km and has been active since ~0.9 Ma, producing syntectonic deposits on the west and an uplifted relief of >100 m on the east. The last activity of the CBF occurred ~2.5 and 9.0 ka and produced a fault slip of ~5 m, inferring an earthquake up to Mw ~7.5. I N T R O D U C T I O N The Andes of South America is a classic example of a non- collisional orogen, related to subduction and developed mainly during the Cenozoic by the convergence of the South American and Nazca Plates (e.g., Jordan et al., 1983; Gutscher et al., 2000; Charrier et al., 2007). This orogen presents a latitudinal morpho- structural segmentation, reflecting variations in subduction angle, convergence rate, basement composition, thickness, climate, and internal structures of the South American Plate, and the presence of oceanic ridges within the Nazca Plate, such as the Juan Fernández Ridge (e.g., Jordan et al., 1983; Gutscher et al.,