Structure of the Ecuadorian Upper Plate From a Joint Seismic‐Gravity Inversion
Date
2025-08-11
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Publisher
Journal of Geophysical Research (JGR): Solid Earth
Abstract
The Ecuadorian portion of the South American subduction zone presents an interesting case study in the structure and complex evolution of an upper plate. There are outstanding questions about its tectonic history, composition, and magmatic processes. While previous studies have employed ambient noise tomography to image the Ecuadorian upper plate, surface wave inversions alone often lack sensitivity at relevant shallow depths. This limitation can be overcome with an independent, complementary data set, such as gravity. We have jointly inverted Rayleigh wave phase velocities and Bouguer gravity anomalies to provide a more detailed seismic velocity model of the Ecuadorian upper plate. Our joint inversion has yielded several key improvements from previous models. First, we observe much shallower slow velocities beneath major basins (the Manabí, Progreso, and Gulf of Guayaquil), better aligning with expected basin structure. Second, we identify a high‐velocity block beneath the entire forearc, corresponding to the Piñon Terrane, with velocities suggesting the presence of ultramafic material. Third, we highlight a new narrow swath of slow velocities beneath the Ecuadorian Andes, which closely follows the active volcanoes along the Eastern Cordillera. The extent of these slow velocities coincides with the termination of active arc volcanism and the predicted location of the subducted Carnegie Ridge. The predicted compositions for the mid to lower crust in the region preclude a purely compositional explanation for these velocities, suggesting that some level of partial melt is necessary.
Description
This article was originally published in Journal of Geophysical Research (JGR): Solid Earth. The version of record is available at: https://doi.org/10.1029/2024JB030667
©2025. Oak Ridge National laboratory, managed by UT‐Battelle, LLC and The Author(s). This is an open access article under the terms of the Creative Commons Attribution License CC BY 4.0, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Citation
Birkey, A., Lynner, C., Chai, C., & Maceira, M. (2025). Structure of the Ecuadorian upper plate from a joint seismic‐gravity inversion. Journal of Geophysical Research: Solid Earth, 130, e2024JB030667. https://doi.org/10.1029/2024JB030667