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

92 PATA Days 2024 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 K E Y W O R D S Morphotectonics, San Ramón Fault, Seismic hazard. (1) Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile. *Email: nicolas.campillay@uchile.cl / geaston@uchile.cl Nicolas Campillay (1) Gabriel Easton (1) QUATERNARY CRUSTAL DEFORMATION AND SEISMIC HAZARD ASSOCIATED WITH THE SAN RAMÓN FAULT IN THE FOOTHILLS OF PIRQUE ( ∼ 33 . 5° S) A B S T R A C T The San Ramón Fault (SRF) is an active reverse fault located in the western foothills of the Andes, passing through a densely urbanized area in Santiago, capital city of Chile. The trace of the SRF has only been described along the eastern border of the Santiago valley, but there is seismological evidence suggesting that it continues southward. The objective of this study is to map the trace of the SRF in the Pirque district, located immediately to the south of Santiago city. The observed features, as fault scarps, other deformed surfaces and associated drainage systems, suggest that the SRF can be mapped on the landscape in the area of Pirque, between the Maipo River and Quebrada Honda, evidencing its continuity for at least ∼18 km more than previously known. This will allow elucidating the real seismic potential of this geological structure in the Metropolitan Region. I N T R O D U C T I O N Santiago is located at the foot of the western flank of the Andes Cordillera. According to the 2017 Census (National Institute of Statictics, 2017), the Metropolitan Region of the capital city of Chile hosts 7,112,808 inhabitants, representing 40.5 % of the national population. This urban center is exposed to natural hazards such as floods, mudslides, and earthquakes (Naranjo & Varela, 1996; Aránguiz, 2018). The SRF is an active geological structure located in the foothills of the Andes, passing through the eastern part of Santiago, and exhibits a west-vergent reverse behavior, uplifting the Andean mountain block over the unconsolidated sediments of the central depression (Armijo et al., 2010; Vargas et al., 2014) (Fig. 1).