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Seismic Imaging of the Ecuadorian Margin Lithosphere Using Teleseismic Receiver Functions Analysis and Ambient Noise Tomography

Description: 

The Ecuadorian margin represent the northern extension of the South America subduction zone, shaped by the accretion of mafic oceanic terranes and the ongoing subduction of the Carnegie Ridge. This region offers an ideal setting to investigate the interactions between subducted ridges and overriding plates, as well as the associated tectonism, magmatism, and seismogenesis. In this study, we present high-resolution imaging of crustal and upper mantle structures beneath the Ecuadorian forearc and Western Cordillera volcanic arc combining teleseismic receiver function analysis and ambient noise tomography. Our dataset includes seismic records from 11 permanent broadband stations from Instituto Geofisico-EPN, 20 temporary broadband stations from IRIS operating between 2016 and 2017, 65 temporary broadband stations operating between 2021 and 2022, and 783 nodal geophones deployed in November 2020 and March 2022.

Our receiver function analysis reveals the slab interface dipping from at ~20–25 km depth near the coastline to ~100 km depth beneath the volcanic arc, with an estimated oceanic crustal thickness of ~15–20 km and a dip angle of ~20–25°. Within the overriding crust, we identify an intra-crustal layer at ~25-35 km and a variable upper plate Moho increasing from ~30 km beneath the forearc to ~50 km beneath the arc. A shallower velocity discontinuity at ~5-8 km depth is observed beneath the Manabí Basin that we interpret as the mafic basement beneath the basin. Our 3-D velocity model from ambient noise highlights significant velocity variations within the Ecuadorian forearc crust. Specifically, we observe two lower-than-surrounding velocity anomalies at depths shallower than 10 km beneath the western Manabí basin and Coastal Cordillera, and Borbon basin. In addition, we see a high velocity anomaly striking north-south along the boundary between accreted forearc terranes and volcanic arc at depths of 20-40 km that likely represents the mafic oceanic accreted terrains at depth. These observations provide important insights into the tectonic, magmatic, and seismogenic evolution of the Ecuadorian subduction zone.

Session: Earth’s Structure from the Crust to the Core - I

Type: Oral

Date: 4/16/2025

Presentation Time: 08:15 AM (local time)

Presenting Author: Cong

Student Presenter: No

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