Geological evidence of an unreported historical Chilean tsunami reveals more frequent inundation

Hocking, Emma, Garrett, Ed, Aedo, Diego, Carvajal, Matías and Melnick, Daniel (2021) Geological evidence of an unreported historical Chilean tsunami reveals more frequent inundation. Communications Earth & Environment, 2 (1). p. 245. ISSN 2662-4435

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Official URL: https://doi.org/10.1038/s43247-021-00319-z

Abstract

Assessing tsunami hazards commonly relies on historical accounts of past inundations, but such chronicles may be biased by temporal gaps due to historical circumstances. As a possible example, the lack of reports of tsunami inundation from the 1737 south-central Chile earthquake has been attributed to either civil unrest or a small tsunami due to deep fault slip below land. Here we conduct sedimentological and diatom analyses of tidal marsh sediments within the 1737 rupture area and find evidence for a locally-sourced tsunami consistent in age with this event. The evidence is a laterally-extensive sand sheet coincident with abrupt, decimetric subsidence. Coupled dislocation-tsunami models place the causative fault slip mostly offshore rather than below land. Whether associated or not with the 1737 earthquake, our findings reduce the average recurrence interval of tsunami inundation derived from historical records alone, highlighting the importance of combining geological and historical records in tsunami hazard assessment.

Item Type: Article
Additional Information: Funding information: This research was funded by the Natural Environment Research Council (New Investigator Award NE/K000446/1), the European Union/Durham University (COFUND under the DIFeREns 2 scheme), the Millennium Scientific Initiative (ICM) of the Chilean Government (Grant Number NC160025 “Millennium Nucleus CYCLO: The Seismic Cycle Along Subduction Zones”), Chilean National Fund for Development of Science and Technology (FONDECYT grants 1190258 and 1181479) and the ANID PIA Anillo ACT192169. Radiocarbon dating support was provided by the Natural Environment Research Council Radiocarbon Facility (1707.0413, 1795.0414 and 2000.0416). LiDAR data were provided by Forestal Arauco under a collaboration agreement. We gratefully acknowledge Steve Moreton for providing the radiocarbon dates from NERC-RCF, Kelin Wang for providing the dislocation model used herein and Neil Tunstall and Chris Longley for help with core scanning. We thank Francisco Villagrán, Carlos Torres, Bill Austin, Martin Brader and Joaquim Otero for help in the field and the staff of the Valdivian coastal reserve for the facilities they provided. All sampling was undertaken with consent from the landowners; permission was acquired verbally. We thank Marco Cisternas for his insights into coastal palaeoseismology and three anonymous reviewers for their constructive comments to improve the paper. This paper forms a contribution to IGCP Projects 639 and 725.
Subjects: F600 Geology
F700 Ocean Sciences
F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: John Coen
Date Deposited: 17 Dec 2021 11:03
Last Modified: 17 Dec 2021 11:15
URI: http://nrl.northumbria.ac.uk/id/eprint/48007

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