Past seismic slip-to-the-trench recorded in Central America megathrust. / Vannucchi, Paola; Spagnuolo, Elena; Aretusini, Stefano; Di Toro, Giulio; Ujiie, Kohtaro; Tsutsumi, Akito; Nielsen, Stefan.

In: Nature Geoscience, Vol. 10, 27.11.2017, p. 935-940.

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  • Paola Vannucchi
  • Elena Spagnuolo
  • Stefano Aretusini
  • Giulio Di Toro
  • Kohtaro Ujiie
  • Akito Tsutsumi
  • Stefan Nielsen

Abstract

The 2011 Tōhoku-Oki earthquake revealed that co-seismic displacement along the plate boundary megathrust can propagate to the trench. Co-seismic slip to the trench amplifies hazards at subduction zones, so its historical occurrence should also be investigated globally. Here we combine structural and experimental analyses of core samples taken offshore from southeastern Costa Rica as part of the Integrated Ocean Drilling Program (IODP) Expedition 344, with three-dimensional seismic reflection images of the subduction zone. We document a geologic record of past co-seismic slip to the trench. The core passed through a less than 1.9-million-year-old megathrust frontal ramp that superimposes older Miocene biogenic oozes onto late Miocene–Pleistocene silty clays. This, together with our stratigraphic analyses and geophysical images, constrains the position of the basal decollement to lie within the biogenic oozes. Our friction experiments show that, when wet, silty clays and biogenic oozes are both slip-weakening at sub-seismic and seismic slip velocities. Oozes are stronger than silty clays at slip velocities of less than or equal to 0.01 m s–1, and wet oozes become as weak as silty clays only at a slip velocity of 1 m s–1. We therefore suggest that the geological structures found offshore from Costa Rica were deformed during seismic slip-to-the-trench events. During slower aseismic creep, deformation would have preferentially localized within the silty clays.
Original languageEnglish
Pages (from-to)935-940
Number of pages6
JournalNature Geoscience
Volume10
DOIs
Publication statusPublished - 27 Nov 2017

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