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    Subduction zone slip variability during the last millennium, south-central Chile


    Dura, Tina and Horton, Benjamin P. and Cisternas, Marco and Ely, Lisa L. and Hong, Isabel and Nelson, Alan R. and Wesson, Robert L. and Pilarczyk, Jessica E. and Parnell, Andrew C. and Nikitina, Daria (2017) Subduction zone slip variability during the last millennium, south-central Chile. Quaternary Science Reviews, 175. pp. 112-137. ISSN 0277-3791

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    Abstract

    The Arauco Peninsula (37°-38°S) in south-central Chile has been proposed as a possible barrier to the along-strike propagation of megathrust ruptures, separating historical earthquakes to the south (1960 AD 1837, 1737, and 1575) and north (2010 AD, 1835, 1751, 1657, and 1570) of the peninsula. However, the 2010 (Mw 8.8) earthquake propagated into the Arauco Peninsula, re-rupturing part of the megathrust that had ruptured only 50 years earlier during the largest subduction zone earthquake in the instrumental record (Mw 9.5). To better understand long-term slip variability in the Arauco Peninsula region, we analyzed four coastal sedimentary sections from two sites (Tirúa, 38.3°S and Quidico, 38.1°S) located within the overlap of the 2010 and 1960 ruptures to reconstruct a ∼600-year record of coseismic land-level change and tsunami inundation. Stratigraphic, lithologic, and diatom results show variable coseismic land-level change coincident with tsunami inundation of the Tirúa and Quidico marshes that is consistent with regional historical accounts of coseismic subsidence during earthquakes along the Valdivia portion of the subduction zone (1960 AD and 1575) and coseismic uplift during earthquakes along the Maule portion of the subduction zone (2010 AD, 1835, 1751). In addition, we document variable coseismic land-level change associated with three new prehistoric earthquakes and accompanying tsunamis in 1470–1570 AD, 1425–1455, and 270–410. The mixed record of coseismic subsidence and uplift that we document illustrates the variability of down-dip and lateral slip distribution at the overlap of the 2010 and 1960 ruptures, showing that ruptures have repeatedly propagated into, but not through the Arauco Peninsula and suggesting the area has persisted as a long-term impediment to slip through at least seven of the last megathrust earthquakes (∼600 years).

    Item Type: Article
    Keywords: Prehistoric earthquakes; Subduction zone segmentation; Tsunami deposits; Diatom paleoecology; Coastal paleoseismology; Coastal hazards;
    Academic Unit: Faculty of Science and Engineering > Mathematics and Statistics
    Faculty of Science and Engineering > Research Institutes > Hamilton Institute
    Item ID: 11748
    Identification Number: https://doi.org/10.1016/j.quascirev.2017.08.023
    Depositing User: Andrew Parnell
    Date Deposited: 18 Nov 2019 17:12
    Journal or Publication Title: Quaternary Science Reviews
    Publisher: Elsevier
    Refereed: Yes
    URI:

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