3D local earthquake tomography of the Ecuadorian margin in the source area of the 2016 Mw 7.8 Pedernales earthquake

León-Ríos, Sergio, Bie, Lidong, Agurto-Detzel, Hans, Rietbrock, Andreas, Galve, Audrey, Alvarado, Alexandra, Beck, Susan, Charvis, Philippe, Font, Yvonne, Hidalgo, Silvana, Hoskins, Mariah, Laigle, Mireille, Oregioni, Davide, Meltzer, Anne, Ruiz, Mario and Woollam, Jack (2021) 3D local earthquake tomography of the Ecuadorian margin in the source area of the 2016 Mw 7.8 Pedernales earthquake. Journal of Geophysical Research: Solid Earth, 126 (3). ISSN 2169-9313

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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 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.

Item Type: Article
Additional Information: Funding Information: This study was supported by IGEPN, IRD, the INSU-CNRS, and the ANR grant REMAKE ANR-15-CE04-0004. The UK portion of the temporary deployment was supported by NERC grant NE/P008828/1. The US portion of the temporary deployment was supported by IRIS PASSCAL and NSF RAPID Program Award EAR-1642498. S.L.-R. acknowledges partial support from ANID under Programa Formaci?n de Capital Humano Avanzado, Becas Chile (grant 8068/2015). H.A.-D. acknowledges support from ANR project ANR-15-CE04-0004 and UCA/JEDI project ANR-15-IDEX-01. We are also indebted to the people at Geoazur laboratories and INOCAR by its contribution in the installation of OBSs at sea in very harsh environments. Also we extend the acknowledgment to the staff at IGEPN for the continuous support during the deployment and service of the inland stations. Finally, the authors want to thank all the people in Ecuador who allowed us to install our stations in their houses, big thanks for your hospitality, patience, and help when it was needed. Publisher Copyright: © 2021. The Authors.
Uncontrolled Keywords: aftershocks,ecuador,megathrust earthquake,seismic tomography,subduction zone,velocity structure,geophysics,geochemistry and petrology,earth and planetary sciences (miscellaneous),space and planetary science,sdg 14 - life below water ,/dk/atira/pure/subjectarea/asjc/1900/1908
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Depositing User: LivePure Connector
Date Deposited: 22 Apr 2022 09:30
Last Modified: 25 May 2022 12:35
URI: https://ueaeprints.uea.ac.uk/id/eprint/84732
DOI: 10.1029/2020JB020701

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