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Seismic and aseismic fault slip during the initiation phase of the 2017 Mw=6.9 Valparaiso earthquake.
  • +3
  • Emmanuel Caballero,
  • Agnes Chounet,
  • Zacharie Duputel,
  • Jorge Jara,
  • Cedric Twardzik,
  • Romain Jolivet
Emmanuel Caballero
Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS, Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS, Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS

Corresponding Author:[email protected]

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Agnes Chounet
Institut de Physique du Globe de Strasbourg, Institut de Physique du Globe de Strasbourg, Institut de Physique du Globe de Strasbourg
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Zacharie Duputel
Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS, Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS, Institut de Physique du Globe de Strasbourg, UMR7516, Université de Strasbourg/EOST, CNRS
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Jorge Jara
Ecole Normale Supérieure de Paris, Ecole Normale Supérieure de Paris, Ecole Normale Supérieure de Paris
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Cedric Twardzik
University of Strasbourg, University of Strasbourg, University of Strasbourg
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Romain Jolivet
Ecole Normale Superieure, Ecole Normale Superieure, Ecole Normale Superieure
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Abstract

Transient deformations associated with foreshocks activity has been observed before large earthquakes, suggesting the occurrence of a detectable pre-seismic slow slip during the initiation phase. In this respect, a critical issue consists in discriminating the relative contributions from seismic and aseismic fault slip during the preparation phase of large earthquakes. We focus on the April-May 2017 Valparaíso earthquake sequence, which involved a Mw=6.9 earthquake preceded by an intense foreshock activity. To assess the relative contribution of seismic and aseismic slip, we compare surface displacements predicted from foreshock source models to the transient motion measured prior to the mainshock. The comparison between observed and predicted displacements shows that only half of the total displacement can be explained by the contribution of foreshocks. This result suggests the presence of aseismic preslip during an initiation phase preceding the mainshock.