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3D local earthquake tomography of the Ecuadorian margin in the source area of the 2016 Mw 7.8 Pedernales earthquake
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  • Sergio León-Ríos,
  • Lidong Bie,
  • Hans Agurto-Detzel,
  • Andreas Rietbrock,
  • Audrey Galve,
  • Alexandra Patricia Alvarado,
  • Susan L. Beck,
  • Philippe Charvis,
  • Yvonne Font,
  • Silvana Hidalgo,
  • Mariah C. Hoskins,
  • Laigle Mireille,
  • Davide Oregioni,
  • Anne S. Meltzer,
  • Mario Calixto Ruiz,
  • Jack Woollam
Sergio León-Ríos
Karlsruhe Institute of Technology, Karlsruhe Institute of Technology

Corresponding Author:[email protected]

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Lidong Bie
Karlsruhe Insitute of Technology, Karlsruhe Insitute of Technology
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Hans Agurto-Detzel
Université Côte d'Azur, Geoazur, Université Côte d'Azur, Geoazur
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Andreas Rietbrock
University of Karlsruhe, University of Karlsruhe
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Audrey Galve
Université de Nice Sophia-Antipolis, IRD, CNRS, Observatoire de la Côte d'Azur, Géoazur, Université de Nice Sophia-Antipolis, IRD, CNRS, Observatoire de la Côte d'Azur, Géoazur
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Alexandra Patricia Alvarado
IG-EPN, IG-EPN
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Susan L. Beck
Geophysics, U. of Arizona, Geophysics, U. of Arizona
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Philippe Charvis
Institut de Recherche pour le Développement, Institut de Recherche pour le Développement
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Yvonne Font
UMR GeoAzur - Nice - France, UMR GeoAzur - Nice - France
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Silvana Hidalgo
Instituto Geofísico-Escuela Politécnica Nacional, Instituto Geofísico-Escuela Politécnica Nacional
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Mariah C. Hoskins
Lehigh University, Lehigh University
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Laigle Mireille
Geoazur CNRS-UMR 6526, Geoazur CNRS-UMR 6526
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Davide Oregioni
Université de Nice Sophia-Antipolis, IRD, CNRS, Observatoire de la Côte d'Azur, Géoazur, Université de Nice Sophia-Antipolis, IRD, CNRS, Observatoire de la Côte d'Azur, Géoazur
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Anne S. Meltzer
Lehigh University, Lehigh University
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Mario Calixto Ruiz
Escuela Politecnica Nacional, Escuela Politecnica Nacional
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Jack Woollam
Karlsruhe Institute of Technology, Karlsruhe Institute of Technology
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Abstract

Based on manually analyzed waveforms recorded by the permanent Ecuadorian network and our large aftershock deployment installed after the Pedernales earthquake, we derive three-dimensional Vp and Vp/Vs structures and earthquake locations for central coastal Ecuador using local earthquake tomography. Images highlight the features in the subducting and overriding plates down to 35 km depth. Vp anomalies (~4.5 – 7.5 km/s) show the roughness of the incoming oceanic crust (OC). Vp/Vs varies from ~1.75 to ~1.94, averaging a value of 1.82 consistent with terranes of oceanic nature. We identify a low Vp (~5.5 km/s) region extending along strike, in the marine forearc. To the North, we relate this low Vp and Vp/Vs (<1.80) region to a subducted seamount that might be part of the Carnegie Ridge (CR). To the South, the low Vp region is associated with high Vp/Vs (>1.85) which we interpret as deeply fractured, probably hydrated OC caused by the CR being subducted. These features play an important role in controlling the seismic behavior of the margin. While subducted seamounts might contribute to the nucleation of intermediate megathrust earthquakes in the northern segment, the CR seems to be the main feature controlling the seismicity in the region by promoting creeping and slow slip events (SSE) offshore that can be linked to the updip limit of large megathrust earthquakes in the northern segment and the absence of them in the southern region over the instrumental period.
Mar 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 3. 10.1029/2020JB020701