Geodetically Inferred Locking State of the Cascadia Megathrust Based on a Viscoelastic Earth Model

DOI Web Site Web Site 被引用文献11件
  • Shaoyang Li
    Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences Potsdam Germany
  • Kelin Wang
    Pacific Geoscience Centre Geological Survey of Canada Sidney British Columbia Canada
  • Yanzhao Wang
    State Key Laboratory of Earthquake Dynamics, Institute of Geology China Earthquake Administration Beijing China
  • Yan Jiang
    Pacific Geoscience Centre Geological Survey of Canada Sidney British Columbia Canada
  • Stan E. Dosso
    School of Earth and Ocean Sciences University of Victoria Victoria British Columbia Canada

書誌事項

公開日
2018-09
権利情報
  • http://onlinelibrary.wiley.com/termsAndConditions#vor
DOI
  • 10.1029/2018jb015620
公開者
American Geophysical Union (AGU)

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説明

<jats:title>Abstract</jats:title><jats:p>In a viscoelastic Earth, stresses slowly built up due to fault locking are relaxed concurrently during the entire interseismic period. This interseismic stress relaxation causes crustal deformation much farther away from the locked fault than can be explained using elastic models that neglect the relaxation. Here we develop a viscoelastic geodetic inversion model to address this problem at Cascadia. We invert ~500 horizontal velocity vectors based on continuous and campaign geodetic measurements over the past two decades. Ambiguities arising from long‐term rotation of upper‐plate crustal blocks are addressed by test‐correcting the geodetic velocities with two different block‐motion models. Fault back slip (i.e., slip deficit) Green's functions are derived using a Maxwell viscoelastic finite element model with realistic subduction zone structure and megathrust geometry. The preferred model features a narrow and shallow megathrust locked zone, consistent with earlier thermorheological reasoning. For an elastic model to fit the data to the same fidelity, megathrust locking has to extend to much greater depths. However, even with the viscoelastic model, the land‐based geodetic data still cannot resolve whether there is some creep (incomplete locking) in the shallowest part of the megathrust far offshore. Neither can the land data fully resolve along‐strike variations of the locking state. These ambiguities can be resolved only when adequate seafloor geodetic data are obtained.</jats:p>

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