Upper-plate structure in Ecuador coincident with the subduction of the Carnegie Ridge and the southern extent of large mega-thrust earthquakes

Colton Lynner, Clinton Koch, Susan L. Beck, Anne Meltzer, Lillian Soto-Cordero, Mariah C. Hoskins, Josh C. Stachnik, Mario Ruiz, Alexandra Alvarado, Philippe Charvis, Yvonne Font, Marc Regnier, Hans Agurto-Detzel, Andreas Rietbrock, Robert W. Porritt

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

The Ecuadorian convergent margin has experienced many large mega-thrust earthquakes in the past century, beginning with a 1906 event that propagated along as much as 500 km of the plate interface. Many subsections of the 1906 rupture area have subsequently produced Mw ≥ 7.7 events, culminating in the 16 April 2016, Mw 7.8 Pedernales earthquake. Interestingly, no large historic events Mw ≥ 7.7 appear to have propagated southward of ∼1°S, which coincides with the subduction of the Carnegie Ridge. We combine data from temporary seismic stations deployed following the Pedernales earthquake with data recorded by the permanent stations of the Ecuadorian national seismic network to discern the velocity structure of the Ecuadorian forearc and Cordillera using ambient noise tomography. Ambient noise tomography extracts Vsv information from the ambient noise wavefield and provides detailed constraints on velocity structures in the crust and upper mantle. In the upper 10 km of the Ecuadorian forearc, we see evidence of the deepest portions of the sedimentary basins in the region, the Progreso and Manabí basins. At depths below 30 km, we observe a sharp delineation between accreted fast forearc terranes and the thick crust of the Ecuadorian Andes. At depths ∼20 km, we see a strong fast velocity anomaly that coincides with the subducting Carnegie Ridge as well as the southern boundary of large mega-thrust earthquakes. Our observations raise the possibility that upper-plate structure, in addition to the subducting Carnegie Ridge, plays a role in the large event segmentation seen along the Ecuadorian margin.

Original languageEnglish (US)
Pages (from-to)1965-1977
Number of pages13
JournalGeophysical Journal International
Volume220
Issue number3
DOIs
StatePublished - Mar 1 2020

Keywords

  • Crustal imaging
  • Crustal structure
  • Seismic noise

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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    Lynner, C., Koch, C., Beck, S. L., Meltzer, A., Soto-Cordero, L., Hoskins, M. C., Stachnik, J. C., Ruiz, M., Alvarado, A., Charvis, P., Font, Y., Regnier, M., Agurto-Detzel, H., Rietbrock, A., & Porritt, R. W. (2020). Upper-plate structure in Ecuador coincident with the subduction of the Carnegie Ridge and the southern extent of large mega-thrust earthquakes. Geophysical Journal International, 220(3), 1965-1977. https://doi.org/10.1093/gji/ggz558