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Global 3D model of mantle attenuation using seismic normal modes
Sujania Talavera-Soza1, Laura Cobden2, Ulrich H Faul3,4
1Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands. s.a.talaverasoza@uu.nl.
Nature
|January 22, 2025
Summary
This study presents the first whole-mantle 3D seismic attenuation model, revealing distinct thermal and compositional structures. It shows upper mantle thermal origins and lower mantle compositional differences, clarifying mantle convection dynamics.
Area of Science:
- Geophysics
- Seismology
- Earth Science
Background:
- Seismic velocity models alone cannot differentiate thermal from compositional origins of Earth's deep structure.
- Understanding mantle convection requires distinguishing between thermal and compositional influences.
- Global 3D attenuation models were previously limited to the upper mantle.
Purpose of the Study:
- To develop a comprehensive 3D global attenuation model for the entire mantle.
- To differentiate thermal and compositional origins of Earth's 3D structure using seismic attenuation.
- To enhance understanding of mantle convection evolution.
Main Methods:
- Utilized whole-Earth seismic oscillations to construct a 3D global attenuation model.
- Constrained seismic attenuation down to spherical harmonics of degree four.
- Integrated seismic wave speeds with attenuation data.
Main Results:
- Confirmed thermal origins in the upper mantle where high attenuation correlates with low velocity.
- Observed the opposite in the lower mantle: high attenuation in seismically fast regions ('ring around the Pacific') and low attenuation in large low-seismic-velocity provinces (LLSVPs).
- Interpreted the circum-Pacific region as colder with smaller grain sizes, contrasting with warmer, larger-grained LLSVPs.
Conclusions:
- The new model provides crucial insights into whole-mantle heterogeneity and convection.
- LLSVPs are confirmed as long-lived, stable features based on inferred temperature and grain size variations.
- The findings advance our understanding of the dynamic processes shaping Earth's mantle.
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