Preprints
https://doi.org/10.5194/egusphere-2024-8
https://doi.org/10.5194/egusphere-2024-8
20 Feb 2024
 | 20 Feb 2024

Co- and postseismic subaquatic evidence for prehistoric fault activity near Coyhaique, Aysén Region, Chile

Morgan Vervoort, Katleen Wils, Kris Vanneste, Roberto Urrutia, Mario Pino, Catherine Kissel, Marc De Batist, and Maarten Van Daele

Abstract. Chilean Patagonia is confronted with several geohazards due to its tectonic setting, i.e., the presence of a subduction zone and numerous fault zones (e.g. the Liquiñe-Ofqui Fault Zone). This region has therefore been the subject of numerous paleoseismological studies. However, this study reveals that the seismic hazard is not limited to these large tectonic structures by identifying past fault activity near Coyhaique in the Aysén Region. Mass wasting deposits in Lago Pollux, a lake located ca. 15 km SW of this region’s capital, were identified through analysis of reflection-seismic data and was linked to a simultaneous event recorded in nearby Lago Castor. Furthermore, a coeval ~50 year-long catchment response was identified in Aysén Fjord based on the multiproxy analysis of a portion of a sediment core. Assuming that this widely recognized event was triggered by an earthquake, ground-motion modelling was applied to derive the most likely magnitude and source fault. The model showed that an earthquake rupture along a local fault, in the vicinity of Lago Pollux and Lago Castor, with a magnitude of 5.6–6.8, is the most likely scenario.

Morgan Vervoort, Katleen Wils, Kris Vanneste, Roberto Urrutia, Mario Pino, Catherine Kissel, Marc De Batist, and Maarten Van Daele

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-8', Renaldo Gastineau, 14 Mar 2024
  • RC2: 'Comment on egusphere-2024-8', Pierre Sabatier, 14 Mar 2024
Morgan Vervoort, Katleen Wils, Kris Vanneste, Roberto Urrutia, Mario Pino, Catherine Kissel, Marc De Batist, and Maarten Van Daele
Morgan Vervoort, Katleen Wils, Kris Vanneste, Roberto Urrutia, Mario Pino, Catherine Kissel, Marc De Batist, and Maarten Van Daele

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Short summary
This study identified a prehistoric earthquake around 4400 years ago near the city of Coyhaique (Aysén Region, Chilean Patagonia) and illustrates the potential seismic hazard in the region. We found deposits in lakes and a fjord that can be related to subaquatic and onshore landslides, all with a similar age, indicating that they were most likely caused by an earthquake. Through modelling we found that this was a magnitude 5.6 to 6.8 earthquake on a fault near the city of Coyhaique.