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Statistical evidence of a seismic quiescence before the Mw8.1 Iquique earthquake, Chile
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  • Florent Aden-Antoniow,
  • Claudio Satriano,
  • Pascal Bernard,
  • Natalia Poiata,
  • El-Madani Aissaoui,
  • Jean-Pierre Vilotte,
  • William Benjamin Frank
Florent Aden-Antoniow
University of Southern California

Corresponding Author:[email protected]

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Claudio Satriano
Institut De Physique Du Globe De Paris
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Pascal Bernard
IPG Paris
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Natalia Poiata
Unknown
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El-Madani Aissaoui
Institut de Physique du Globe de Paris
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Jean-Pierre Vilotte
Institut De Physique Du Globe De Paris
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William Benjamin Frank
University of Southern California
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Abstract

The 2014 Iquique seismic crisis (Chile), culminating with a Mw 8.1 earthquake, April 1st, highlights a complex unlocking of the North Chile subduction interface which has been considered as a seismic gap since 1877. During the year preceding this event, at least three seismic clusters were observed: in July 2013 and January and March 2014. These clusters possibly indicate aseismic slip transients accompanying the progressive destabilization of the plate contact. Recent studies have proposed large-scale slab deformation as a potential trigger for the megathrust earthquake; However, no evidence of gradual unlocking of the interface or transient deformation has yet been found in the seismic rate. To address this question, we develop a dense earthquake catalog during the fifteen months preceding the mainshock from the continuous waveform dataset recorded by the Integrated Plate Boundary Observatory Chile (IPOC) and Iquique Local Network (ILN) networks. After declustering the seismicity, a space-time analysis highlights a large-scale acceleration of the seismicity along the interface while it decelerates at intermediate-depths. We then demonstrate the existence of a seismic quiescence down-dip of the mainshock rupture before the July 2013 cluster. We propose that this seismic quiescence is related to fluid circulation and/or aseismic motion along upper-plate crustal fault(s).