Seismic Properties of the Upper Mantle

The upper mantle plays a central role in Earth’s dynamic evolution, acting as both a conveyor of tectonic plates and a reservoir for geochemical processes. Seismologists probe this region using body and surface waves to determine variations in shear‐wave velocity, attenuation and anisotropy. Elastic properties are sensitive to temperature, composition, water content and partial melt, yielding a characteristic low‐velocity zone beneath the rigid lithosphere. Sharp velocity reductions and high attenuation near the lithosphere–asthenosphere boundary mark mechanical decoupling that governs plate motion. Seismic discontinuities at ∼410 km and ∼660 km depths reflect mineral phase changes, while anisotropic signatures record mantle flow patterns. Together, these observations constrain convection models, illuminate the distribution of water and melt, and inform assessments of geohazards and resource exploration.

Research from Nature Portfolio

Recent studies have shown that thermal buoyancy driven by lithospheric heating and thinning can produce asymmetric seafloor depths across spreading ridges. Seismic models derived from Rayleigh wave measurements reveal that one flank of a ridge may appear thermally younger and shallower due to enhanced lithospheric temperatures and reduced rigidity. This contrasts with regions where deeper asthenospheric buoyancy alone cannot account for observed topography. Such work underscores the sensitivity of surface morphology to lateral variations in upper mantle temperatures and highlights the interplay between tectonic plate age, thermal structure and seismic velocity.

Seismic Properties of the Upper Mantle publication trend

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

Technical terms

Seismic attenuation (Q−1): measure of energy loss of seismic waves as they propagate.

Low‐velocity zone (LVZ): region beneath the lithosphere where seismic wave speeds are decreased due to temperature, composition or partial melt.

Rayleigh waves: surface seismic waves sensitive to shear‐wave structure in the crust and upper mantle.

Anisotropy: directional dependence of seismic wave speed caused by aligned minerals or flow‐induced fabric.

Lithosphere–asthenosphere boundary (LAB): mechanical and rheological transition between rigid tectonic plates and underlying ductile mantle.

References

1. Asymmetric seafloor depth across the Juan de Fuca Ridge caused by lithospheric heating. Communications Earth & Environment (2023).
2. Effect of water on seismic attenuation of the upper mantle: The origin of the sharp lithosphere–asthenosphere boundary. Proceedings of the National Academy of Sciences of the United States of America (2023).
3. Grain size reduction by plug flow in the wet oceanic upper mantle explains the asthenosphere's low seismic Q zone. Earth and Planetary Science Letters (2023).
4. Seismic Structure of the Lithosphere‐Asthenosphere System Beneath the Oldest Seafloor Revealed by Rayleigh‐Wave Dispersion Analysis. Journal of Geophysical Research: Solid Earth (2023).