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Published January 2024 | Published
Journal Article Open

Africa's Crustal Architecture Inferred From Probabilistic and Perturbational Inversion of Ambient Noise: ADAMA

Olugboji, Tolulope ORCID icon
Xue, Siyu
Legre, Jean‐Joel ORCID icon
Tamama, Yuri ORCID icon

Abstract

Africa's continental crust hosts a variety of geologic terrains and is crucial for understanding the evolution of its longest‐lived cratons. However, few of its seismological models are yet to incorporate the largest continent‐wide noise dispersion data sets. Here, we report on new insights into Africa's crustal architecture obtained using a new data set and model assessment product, ADAMA, which comprises a large ensemble of short‐period surface wave dispersion measurements: 5–40 s. We construct a continent‐wide model of Africa's Crust Evaluated with ADAMA's Rayleigh Phase maps (ACE‐ADAMA‐RP). Dispersion maps, and uncertainties, are obtained with a probabilistic approach. This model update, and a crustal taxonomy derived from unsupervised machine learning, reveals that the architecture of Africa's crust can be classified into two main types: primitive (C1: faster velocities with little gradients) and modified (C2–C4: slower velocities in the shallow crust with more pronounced gradients). The Archean shields are "primitive," showing little variation or secular evolution. The basins, orogens, and continental margins are "modified" and retain imprints of surface deformation. The crustal taxonomy is obtained without a‐priori geological information and differs from previous classification schemes. While most of our reported features are robust, probabilistic modeling suggests caution in the quantitative interpretations where illumination is compromised by low‐quality measurements, sparse coverage or both. Future extension of our approach to other complementary seismological and geophysical data sets—for example, multimode earthquake dispersion, receiver functions, gravity, and mineral physics, will enable continent‐wide lithospheric modeling that extends resolution to the upper mantle.

Copyright and License (English)

© 2024 The Authors. Geochemistry, Geophysics, Geosystems published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution andr eproduction in any medium, provided the original work is properly cited and is not used for commercial purposes

Acknowledgement (English)

This work was made possible by the National Science Foundation under Grant 2102495. We thank the Incorporated Research Institutions for Seismology, whose internship program allowed Tamama to pursue this research We thank Siyu Xue, for computing the ambient noise cross correlations for all station pairs and providing us with the Love and Rayleigh wave dispersion measurements crucial to this project. We thank Baowei Liu for his assistance in preparing our inversions. We thank the University of Rochester's Center for Integrated Research Computing (CIRC), for providing us with the computational support and resources for this project. We also thank Carl Schmidtman and Miki Nakajima for generously allocating us with additional computational resources. We acknowledge many helpful discussions with Lara Wagner, Baowei Liu, Ziqi Zhang, Walter Hennings, Enting Zhou, Sayan Swar, Steve Carr, Canberk Eckmecki. This work used Bridges2 at Pittsburgh Supercomputing Center (PSC) and Expanse at San Diego Supercomputer Center (SDSC) through allocation EES220030 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program Boerner et al. (2023), which is supported by National Science Foundation Grants #2138259, #2138286, #2138307, #2137603, and #2138296.

Data Availability (English)

No seismic data was used in this study. The full catalog of dispersion measurements can be obtained from Xue and Olugboji (2021) and was published alongside (Olugboji & Xue, 2022). A digital format of the probabilistic surface wave dispersion maps and the shear velocity model of Africa's Crust Evaluated using the ADAMA Rayleigh wave Phase dispersion (ACE-ADAMA-RP) is available at (Xue, 2023).

Supporting Information S1

Files

Geochem Geophys Geosyst - 2024 - Olugboji - Africa s Crustal Architecture Inferred From Probabilistic and Perturbational.pdf

Additional details

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June 24, 2024
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