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Coseismic seafloor deformation in the trench region during the Mw8.8 Maule megathrust earthquake

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      Abstract

      The Mw 8.8 megathrust earthquake that occurred on 27 February 2010 offshore the Maule region of central Chile triggered a destructive tsunami. Whether the earthquake rupture extended to the shallow part of the plate boundary near the trench remains controversial. The up-dip limit of rupture during large subduction zone earthquakes has important implications for tsunami generation and for the rheological behavior of the sedimentary prism in accretionary margins. However, in general, the slip models derived from tsunami wave modeling and seismological data are poorly constrained by direct seafloor geodetic observations. We difference swath bathymetric data acquired across the trench in 2008, 2011 and 2012 and find ~3–5 m of uplift of the seafloor landward of the deformation front, at the eastern edge of the trench. Modeling suggests this is compatible with slip extending seaward, at least, to within ~6 km of the deformation front. After the Mw 9.0 Tohoku-oki earthquake, this result for the Maule earthquake represents only the second time that repeated bathymetric data has been used to detect the deformation following megathrust earthquakes, providing methodological guidelines for this relatively inexpensive way of obtaining seafloor geodetic data across subduction zone.

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      Most cited references 32

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      Earthquakes and friction laws

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        Loci and maximum size of thrust earthquakes and the mechanics of the shallow region of subduction zones

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          Coseismic and postseismic slip of the 2011 magnitude-9 Tohoku-Oki earthquake.

          Most large earthquakes occur along an oceanic trench, where an oceanic plate subducts beneath a continental plate. Massive earthquakes with a moment magnitude, M(w), of nine have been known to occur in only a few areas, including Chile, Alaska, Kamchatka and Sumatra. No historical records exist of a M(w) = 9 earthquake along the Japan trench, where the Pacific plate subducts beneath the Okhotsk plate, with the possible exception of the ad 869 Jogan earthquake, the magnitude of which has not been well constrained. However, the strain accumulation rate estimated there from recent geodetic observations is much higher than the average strain rate released in previous interplate earthquakes. This finding raises the question of how such areas release the accumulated strain. A megathrust earthquake with M(w) = 9.0 (hereafter referred to as the Tohoku-Oki earthquake) occurred on 11 March 2011, rupturing the plate boundary off the Pacific coast of northeastern Japan. Here we report the distributions of the coseismic slip and postseismic slip as determined from ground displacement detected using a network based on the Global Positioning System. The coseismic slip area extends approximately 400 km along the Japan trench, matching the area of the pre-seismic locked zone. The afterslip has begun to overlap the coseismic slip area and extends into the surrounding region. In particular, the afterslip area reached a depth of approximately 100 km, with M(w) = 8.3, on 25 March 2011. Because the Tohoku-Oki earthquake released the strain accumulated for several hundred years, the paradox of the strain budget imbalance may be partly resolved. This earthquake reminds us of the potential for M(w) ≈ 9 earthquakes to occur along other trench systems, even if no past evidence of such events exists. Therefore, it is imperative that strain accumulation be monitored using a space geodetic technique to assess earthquake potential.
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            Author and article information

            Affiliations
            [1 ]Departamento de Geofísica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile , Santiago, Chile
            [2 ]Scripps Institution of Oceanography, University of California , San Diego, CA, USA
            [3 ]College of Earth, Ocean and Atmospheric Sciences, Oregon State University , Corvallis, OR, USA
            [4 ]GEOMAR – Helmholtz-Centre for Ocean Research , Kiel, Germany
            [5 ]Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso , Valparaíso, Chile
            [6 ]Lamont-Doherty Earth Observatory, Columbia University , New York, NY, USA
            Author notes
            Journal
            Sci Rep
            Sci Rep
            Scientific Reports
            Nature Publishing Group
            2045-2322
            05 April 2017
            2017
            : 7
            28378757
            5381107
            srep45918
            10.1038/srep45918
            Copyright © 2017, The Author(s)

            This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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