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Updated: Aug 26, 2025
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Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling
Published on: August 5, 2016
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Crust-mantle decoupling beneath Afar revealed by Rayleigh-wave tomography
Utpal Kumar1, Cédric P Legendre2
1Berkeley Seismological Laboratory, University of California, Berkeley, 307 McCone Hall #4760, Berkeley, CA, 94720-4760, USA.
Scientific Reports
|October 11, 2022
Summary
Seismic data reveal distinct seismic anisotropy layers in the East African Rift System. Crustal anisotropy varies from rift-parallel to rift-normal, while lithospheric mantle anisotropy differs, indicating mechanical decoupling.
Area of Science:
- Geophysics and Tectonics
- Seismology
- Plate Dynamics
Background:
- The Afar triple junction is a key area for understanding diverging plate dynamics between the Arabian, Nubian, and Somalian plates.
- Previous geodetic analyses agree with shear-wave splitting measurements, but vertical anisotropy layering remains unclear.
Purpose of the Study:
- To map Rayleigh-wave azimuthal anisotropy in the crust and lithospheric mantle beneath the East African Rift System using earthquake seismic data.
- To investigate the vertical layering of seismic anisotropy in this tectonically active region.
Main Methods:
- Analysis of earthquake seismic data.
- Mapping of Rayleigh-wave azimuthal anisotropy at various periods to probe different depths (crust and lithospheric mantle).
- Comparison of seismic anisotropy patterns with surface motion from geodetic analyses.
Main Results:
- Evidence for layered anisotropy around the East African Rift System.
- Crustal anisotropy shows rift-parallel orientation near the rift and rift-normal orientation in the central rift at shorter periods.
- Lithospheric mantle anisotropy exhibits a significantly different pattern at longer periods.
Conclusions:
- The crust and lithospheric mantle beneath the East African Rift System appear to be mechanically decoupled.
- Complex crustal and lithospheric dynamics are suggested in the Afar triple junction region.
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