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

480 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 lacustrine paleoseismology, subduction zone, intraslab earthquakes, Central Chile (1) Renard Centre of Marine Geology, Department of Geology, Ghent University, Ghent, Belgium. (2) Institute of Geology, University of Innsbruck, Innsbruck, Austria. (3) Instituto de Geografía, Pontifícia Universidad Católica de Chile, Santiago, Chile (4) Departamento de Química Ambiental, Universidad Católica de la Santísima Concepción, Concepción, Chile (5) Instituto de Geografía, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile (6) Instituto Pirenaico de Ecología (IPE-CSIC), Zaragoza, Spain *Email: Maarten.vandaele@ugent.be Maarten Van Daele (1) Daan Croenen (1) Katleen Wils (1,2) Arne Ramisch (2) Magdalena Fuentealba (3) Jasper Moernaut (2) Matías Frugone-Álvarez (4) Marco Cisternas (5) Blas Valero-Garcés (6) THE 600 YR LAGUNA LO ENCAÑADO PALEOSEISMIC ARCHIVE: A SHAKING RECORD FOR SANTIAGO DE CHILE A B S T R A C T Subduction zones host megathrust (interplate), crustal and intraslab (intraplate) earthquakes. Based on the recent history, central Chile, where most of the country's population lives, is subjected to all three. However, while megathrust earthquake history can be relatively easily reconstructed using coastal records, this is much more complex for relatively small crustal earthquakes and especially intraslab earthquakes. As lakes record earthquake shaking, they can record these different types of earthquakes, and thus provide an opportunity to also produce intraplate paleoseismic records. The Laguna Lo Encañado sediments potentially allow distinguishing interplate- from intraplate-sourced shaking. Here we present preliminary interpretations from a 600-year long record from Laguna Lo Encañado. Although precise age modelling is challenging, the lake likely recorded all major historical earthquakes and few prehistoric events, some of which had an intraplate source. I N T R O D U C T I O N In subduction zone settings the seismic hazard does not only come from interplate (megathrust) earthquakes, but also intraplate earthquakes of intermediate depth within the subducting oceanic slab (intraslab) and shallow crustal earthquakes (Leyton et al., 2010). Recent damaging intraslab earthquakes in Mexico (2017 Mw8.2 Chiapas) (Segou and Parsons, 2018) and Alaska (2018 Mw7.1 Anchorage) (West et al., 2019) remind us of the significant hazard they pose and how little we know about their behavior (recurrence, magnitude). In Chile, the most striking example is the 1939 Ms7.8 Chillán – intraslab – earthquake, the country's deadliest (Beck et al., 1998; Roland et al., 2020). This