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First Field Evidence of Coseismic Land‐Level Change Associated with the 25 December 2016 Mw 7.6 Chiloé, Chile, Earthquake

2018; Seismological Society of America; Volume: 109; Issue: 1 Linguagem: Inglês

10.1785/0120180173

1943-3573

Ed Garrett, Martin Brader, Daniel Melnick, Jonathan Bedford, Diego Aedo,

Tropical and Extratropical Cyclones Research

Research Article| November 06, 2018 First Field Evidence of Coseismic Land‐Level Change Associated with the 25 December 2016 Mw 7.6 Chiloé, Chile, Earthquake Ed Garrett; Ed Garrett aDepartment of Geography, Durham University, South Road, Durham DH1 3LE, United Kingdom, edmund.garrett@durham.ac.uk Search for other works by this author on: GSW Google Scholar Martin Brader; Martin Brader aDepartment of Geography, Durham University, South Road, Durham DH1 3LE, United Kingdom, edmund.garrett@durham.ac.uk Search for other works by this author on: GSW Google Scholar Daniel Melnick; Daniel Melnick bInstituto de Ciencias de la Tierra, TAQUCh, Universidad Austral de Chile, Valdivia 511430, ChiledAlso at Millennium Nucleus The Seismic Cycle Along Subduction Zones, Valdivia, Concepción, Valparaíso, Chile. Search for other works by this author on: GSW Google Scholar Jonathan Bedford; Jonathan Bedford cGFZ German Research Centre for Geosciences, Telegrafenberg, Building C, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Diego Aedo Diego Aedo bInstituto de Ciencias de la Tierra, TAQUCh, Universidad Austral de Chile, Valdivia 511430, Chile Search for other works by this author on: GSW Google Scholar Author and Article Information Ed Garrett aDepartment of Geography, Durham University, South Road, Durham DH1 3LE, United Kingdom, edmund.garrett@durham.ac.uk Martin Brader aDepartment of Geography, Durham University, South Road, Durham DH1 3LE, United Kingdom, edmund.garrett@durham.ac.uk Daniel Melnick bInstituto de Ciencias de la Tierra, TAQUCh, Universidad Austral de Chile, Valdivia 511430, ChiledAlso at Millennium Nucleus The Seismic Cycle Along Subduction Zones, Valdivia, Concepción, Valparaíso, Chile. Jonathan Bedford cGFZ German Research Centre for Geosciences, Telegrafenberg, Building C, 14473 Potsdam, Germany Diego Aedo bInstituto de Ciencias de la Tierra, TAQUCh, Universidad Austral de Chile, Valdivia 511430, Chile Publisher: Seismological Society of America First Online: 06 Nov 2018 Online Issn: 1943-3573 Print Issn: 0037-1106 © Seismological Society of America Bulletin of the Seismological Society of America (2019) 109 (1): 87–98. https://doi.org/10.1785/0120180173 Article history First Online: 06 Nov 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ed Garrett, Martin Brader, Daniel Melnick, Jonathan Bedford, Diego Aedo; First Field Evidence of Coseismic Land‐Level Change Associated with the 25 December 2016 Mw 7.6 Chiloé, Chile, Earthquake. Bulletin of the Seismological Society of America 2018;; 109 (1): 87–98. doi: https://doi.org/10.1785/0120180173 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract Assessments of megathrust earthquake rupture patterns provide fundamental insights into the processes that control the seismic cycle along subduction zones. When large earthquakes occur in regions with sparse geodetic networks, as was the case for the magnitude (⁠Mw⁠) 7.6 Chiloé, Chile, earthquake of 25 December 2016, estimates of vertical coseismic deformation from fixed intertidal biotic indicators provide important evidence that help to constrain fault slip. Ten months after the Chiloé earthquake, we observed a white fringe of bleached coralline algae (Corallinaceae) along the southeastern coastline of Isla Quilán, south of Isla de Chiloé, killed by reduced tidal wetting resulting from coseismic land uplift. Our quantitative measurements of the vertical extent of algal mortality provide the first field‐based report of the effects of the 2016 earthquake. We infer Isla Quilán coseismically uplifted by 25.8±14.3 cm⁠. The vertical extent of mortality (VEM) and the aspect (compass direction) of the bedrock surface are uncorrelated, but we find that exposure to waves and shielding from insolation may prevent or delay mortality. Focusing on sites sheltered from waves, we demonstrate that with a large number of measurements (⁠>100⁠), land‐level changes as low as 25 cm may be quantitatively assessed. The absence of bleaching on Isla de Chiloé may reflect the smaller magnitude of coseismic uplift at this location or the lack of suitably sheltered bedrock surfaces. Previously published fault dislocation models are consistent with our field observations; however, the coralline algae data are on their own insufficient to discriminate between competing hypotheses over the amount of fault slip. By combining our field data with space geodetic data in a model that uses detailed fault geometry, we constrain peak slip to ∼3 m⁠, approximately 80% of the maximum cumulative plate convergence since the last great earthquake in the region. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.