Seismic Tomography of Earth's Mantle Dynamics

Seismic tomography utilises the travel times, amplitudes and waveforms of seismic waves generated by earthquakes or artificial sources to image the three-dimensional structure of the Earth’s mantle. Variations in seismic velocity and anisotropy reveal compositional heterogeneities, temperature anomalies and flow patterns that underpin mantle convection. This method has illuminated the geometry of subducted slabs descending from oceanic trenches, the roots of upwelling plumes beneath hotspots, and the large low-shear velocity provinces (LLSVPs) that bracket the core–mantle boundary. Advances in waveform modelling, multifrequency inversions and global datasets have extended resolution into the mid-mantle and lower mantle, clarifying the interplay between thermal, chemical and mechanical processes. Tomographic images now guide dynamic models of plate motions, plume generation and deep carbon cycling, informing our understanding of volcanic hazards, continental drift and the thermal evolution of our planet.

Research from Nature Portfolio

Recent studies have traced a long-lived subduction-modified mantle anomaly beneath the Southern Atlantic-Southwest Indian ridges, demonstrating that a Jurassic flat-slab event displaced chemically distinctive mantle domains by over 2 000 km. This “asthenospheric anomaly telescoping” model integrates seismic tomographic constraints with plate kinematic reconstructions, offering a novel mechanism for recycling ancient geochemical signatures into modern mid-ocean ridge basalts. Another investigation has used ab initio calculations to determine the elastic properties and density of subducted oceanic crust at lower-mantle conditions, linking phase transitions in silica to mid-mantle scatterers and explaining transitions between low- and high-velocity anomalies observed in tomographic models. Complementing these insights, observations of anomalous splitting in Stoneley modes at the core–mantle boundary have revealed that the large low-shear velocity provinces are characterised by lower density than the surrounding mantle, bolstering hypotheses of chemical heterogeneity or post-perovskite enrichment in these deep thermochemical piles.

Seismic Tomography of Earth's Mantle Dynamics publication trend

The graph below shows the total number of articles in seismic tomography of earth's mantle dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Seismic tomography: Technique that uses seismic waves to construct three-dimensional images of Earth's interior.

Mantle convection: Slow, creeping motion of mantle rock driven by thermal and compositional buoyancy.

Radial anisotropy: Variation in seismic wave speed with direction, indicative of aligned minerals or flow.

Large Low Shear Velocity Provinces (LLSVPs): Two extensive, slow-velocity regions at the base of the mantle beneath Africa and the Pacific.

Pdiff waves: Seismic waves that have diffracted along the core–mantle boundary, probing the lowermost mantle.

Stoneley modes: Free oscillations sensitive to velocity and density variations at the core–mantle boundary.

References

1. Ghost-arc geochemical anomaly at a spreading ridge caused by supersized flat subduction. Nature Communications (2023).
2. Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities. Nature Communications (2020).
3. Density structure of Earth’s lowermost mantle from Stoneley mode splitting observations. Nature Communications (2017).
4. Whole-mantle radially anisotropic shear velocity structure from spectral-element waveform tomography. Geophysical Journal International (2014).
5. Global mantle structure from multifrequency tomography using P, PP and P-diffracted waves. Geophysical Journal International (2019).
6. Confirmation of a change in the global shear velocity pattern at around 1000 km depth. Geophysical Journal International (2017).