Seismic Imaging of Mantle Transition Zone Discontinuities

The mantle transition zone, extending between depths of roughly 410 km and 660 km, marks major mineralogical transformations that govern the thermal and chemical evolution of Earth’s interior. Seismic imaging techniques exploit the contrast in seismic wave speed across these phase boundaries to map their topography, thickness and lateral variations. Variations in the depths of the 410-km and 660-km discontinuities are indicative of temperature anomalies, compositional heterogeneities and the presence of melt or fluids. Traditional methods such as receiver‐function analysis and SS‐precursor timing remain indispensable for global surveys, while novel full‐waveform and wave‐equation‐based approaches provide enhanced resolution of subtle reflectors within and below the transition zone. Together, these techniques have revealed thinned or thickened transition‐zone regions beneath hotspots, subduction zones and cratonic keels, elucidating mantle dynamics, plume–slab interactions and the distribution of volatiles in the deep Earth. The global significance of these findings extends from constraining the convective regime and water budget of the mantle to understanding the geochemical reservoirs that feed volcanic eruptions at the surface.

Research from Nature Portfolio

Recent studies using advanced wave‐equation imaging have uncovered both classic transition‐zone discontinuities and deeper mid‐mantle reflectors. One investigation applied reverse‐time migration to early arrivals of surface‐reflected body waves and revealed a thinned transition zone southeast of Hawaii alongside a distinct reflector at approximately 1 000 km depth, interpreted as an impedance reversal linked to deflected mantle plumes. In a separate subduction‐zone setting, synthetic matching of P and sP triplicated waveforms beneath the Hindu Kush imaged a laterally variable low‐velocity layer atop the 410 km discontinuity, attributed to partial melt induced by a deeply penetrating slab and exhibiting anomalously low viscosity. Foundational global surveys of mid‐mantle reflectors have also demonstrated widespread compositional and viscosity contrasts at depths between 800 km and 1 300 km, delineating domains of thermochemical piles, slab stagnation and neutral regions where heterogeneous reflectors signal long‐lived chemical layering.

Seismic Imaging of Mantle Transition Zone Discontinuities publication trend

The graph below shows the total number of articles in seismic imaging of mantle transition zone discontinuities across all publications each year (not limited to Nature Index journals).

Technical terms

Mantle transition zone: The depth interval between the 410 km and 660 km seismic discontinuities where olivine transforms to denser phases.

410-km discontinuity: Seismic boundary caused by the transition of olivine to wadsleyite, sensitive to temperature and chemistry.

660-km discontinuity: Boundary marking the breakdown of ringwoodite to bridgmanite and ferropericlase, controlled by pressure and composition.

Receiver function: Seismic analysis method that isolates converted P-to-S or S-to-P phases to image discontinuities beneath a station.

SS precursor: Early-arriving seismic phase reflected from mantle discontinuities observed before the main SS arrival in surface waves.

Reverse‐time migration: Full‐wave imaging technique that back‐propagates seismic wavefields to locate reflectors with high fidelity.

References

1. Seismic evidence for a 1000 km mantle discontinuity under the Pacific. Nature Communications (2023).
2. Upper mantle melt caused by a subducted slab in the Indian-Eurasian continental subduction zone. Communications Earth & Environment (2023).
3. Depressed mantle discontinuities beneath Iceland: Evidence of a garnet controlled 660 km discontinuity?. Earth and Planetary Science Letters (2016).
4. Global observations of reflectors in the mid-mantle with implications for mantle structure and dynamics. Nature Communications (2018).
5. Pervasive seismic low-velocity zones within stagnant plates in the mantle transition zone: Thermal or compositional origin?. Earth and Planetary Science Letters (2017).