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

326 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 Turbidite, South-Central Chile, tsunami deposit, megathrust earthquake (1) Institute of Geology, University of Innsbruck, Innsbruck, Austria. (21) Renard Centre of Marine Geology, Department of Geology, Ghent University, Ghent, Belgium. (3) Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria. (4) EDYTEM, Université Savoie Mont-Blanc, CNRS, Le Bourget-du- Lac, France. (5) Laboratoire G-TIME (CP 160/02), Department of Geosciences, Université Libre de Bruxelles, Brussels, Belgium. (6) Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile. (7) Faculty of Environmental Sciences, University of Concepción, Concepción, Chile. *Email: Jasper.Moernaut@uibk.ac.at Jasper Moernaut (1) Katleen Wils (1,2) Evelien Boes (2) Markus Niederstätter (1) Valentina Moreno Allende (1) Maarten Van Daele (2) Jürgen Konzett (3) Ariana Molenaar (1) Pierre Sabatier (4) Renaldo Gastineau (4) Karen Fontijn (5) Marc De Batist (2) Roberto Urrutia (7) Mario Pino (6) Daniel Melnick (6) RECONSTRUCTING MEGATHRUST RUPTURE VARIABILITY DURING THE PAST ~800 YEARS USING A TRANSECT OF LACUSTRINE SEDIMENTARY RECORDS IN SOUTH-CENTRAL CHILE A B S T R A C T Historical and paleoseismic data from South-Central Chile (38- 46°S) revealed an ~320 yr recurrence rate for the predecessors of the giant 1960 earthquake (Mw 9.5), which ruptured the subduction megathrust over ~1000 km. Earthquakes in 1837, 1737 and ca. 1460 ruptured smaller portions of the megathrust, but their extent remains unclear. Here, we present the sedimentary imprints of full and partial megathrust ruptures in a transect of eight lakes at the foot of the Andean Cordillera. Based on the relative imprint size compared to that of the 1960 and 2010 events, we reconstruct the pattern of seismic intensity for the partial ruptures. Moreover, we complement this reconstruction with a new paleotsunami record (40°S) from Laguna Gemela West, suggesting that a tsunami occurred during the 1737 event. New insights into rupture variability can thus be obtained by integrating different types of sedimentary records (paleotsunami, subsidence/uplift, shaking). I N T R O D U C T I O N Along the Valdivia Segment (38-46°S) of the Chilean subduction zone, giant megathrust ruptures extending for ~1000 km occurred in 1960 (Mw 9.5) and 1575 (Fig. 1). Paleoseismic and -tsunami data show an average recurrence rate of ~320 years for the predecessors of the 1960 event (Cisternas et al., 2005; Kempf et al., 2017; Moernaut et al., 2018; Wils et al., 2020). Between these events, great partial ruptures such as in 1837 and 1737 have been