Deep postseismic viscoelastic relaxation excited by an intraslab normal fault earthquake in the Chile subduction zone

Bie, Lidong, Ryder, Isabelle and Métois, Marianne (2017) Deep postseismic viscoelastic relaxation excited by an intraslab normal fault earthquake in the Chile subduction zone. Tectonophysics, 712-713. pp. 729-735. ISSN 0040-1951

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Abstract

The 2005 Mw 7.8 Tarapaca earthquake was the result of normal faulting on a west-dipping plane at a depth of ~ 90 km within the subducting slab down-dip of the North Chilean gap that partially ruptured in the 2014 M 8.2 Iquique earthquake. We use Envisat observations of nearly four years of postseismic deformation following the earthquake, together with some survey GPS measurements, to investigate the viscoelastic relaxation response of the surrounding upper mantle to the coseismic stress. We constrain the rheological structure by testing various 3D models, taking into account the vertical and lateral heterogeneities in viscosity that one would expect in a subduction zone environment. A viscosity of 4–8 × 1018 Pa s for the continental mantle asthenosphere fits both InSAR line-of-sight (LOS) and GPS horizontal displacements reasonably well. In order to test whether the Tarapaca earthquake and associated postseismic relaxation could have triggered the 2014 Iquique sequence, we computed the Coulomb stress change induced by the co- and postseismic deformation following the Tarapaca earthquake on the megathrust interface and nodal planes of its M 6.7 foreshock. These static stress calculations show that the Tarapaca earthquake may have an indirect influence on the Iquique earthquake, via loading of the M 6.7 preshock positively. We demonstrate the feasibility of using deep intraslab earthquakes to constrain subduction zone rheology. Continuing geodetic observation following the 2014 Iquique earthquake may further validate the rheological parameters obtained here.

Item Type: Article
Additional Information: Publisher Copyright: © 2017 Elsevier B.V.
Uncontrolled Keywords: geodetic observation,normal faulting earthquake,subduction zone rheology,tarapaca,viscoelastic relaxation,geophysics,earth-surface processes ,/dk/atira/pure/subjectarea/asjc/1900/1908
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Depositing User: LivePure Connector
Date Deposited: 25 Apr 2022 10:30
Last Modified: 25 Apr 2022 10:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/84776
DOI: 10.1016/j.tecto.2017.07.012

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