Crustal Dynamics and Seismic Anisotropy in the Tibetan Plateau

The Tibetan Plateau, the world’s highest and most extensive highland, owes its elevation to the ongoing collision between the Indian and Eurasian plates. This convergence drives crustal shortening, thickening and lateral extrusion of crustal blocks. Beneath this complex terrain, seismic anisotropy—the variation of seismic wave speeds with direction—reveals patterns of mineral alignment and flow within the crust and upper mantle. Interpreting these anisotropic signatures provides insight into crust–mantle coupling, the mechanisms of crustal flow, and the localisation of deformation along major fault zones. Variations in anisotropy across eastern Tibet, the Songpan–Ganzi terrane and the Sichuan Basin highlight contrasts between mechanically coupled and decoupled regions, while experiments on mineral fabrics link microscopic preferred orientations to large-scale seismic observations. Together, these strands of research illuminate how deep dynamics control surface uplift, mountain building and seismic hazard on a continental scale.

Research from Nature Portfolio

Experimental work on amphibolite under high pressure and temperature has demonstrated how simple shear produces distinct crystal preferred orientations in amphibole, yielding strong anisotropy that can account for anomalous seismic signals in the deep crust and subducting slabs beneath Tibet. This study establishes a mineral-scale mechanism for observed directional dependence of shear-wave speeds.

High-resolution GPS mapping across south-eastern Tibet has defined three-dimensional velocity fields that constrain ongoing N–S shortening, block extrusion and vertical crustal motions. The data reveal differential uplift rates—ranging from 1 mm yr–1 to nearly 9 mm yr–1—and link high strain along the Longmenshan fault to intracontinental subduction of the Yangtze Craton, shedding light on the relationship between deep processes and surface deformation.

Surface-wave tomography has been used to map Rayleigh-wave azimuthal anisotropy at different periods beneath eastern Tibet. Short-period anisotropy, sampling the crust, aligns with eastward crustal flow, whereas long-period anisotropy, sampling the lithospheric mantle, corresponds to absolute plate motion. These contrasting patterns demonstrate mechanical decoupling between the crust and lithospheric mantle beneath the plateau.

Crustal Dynamics and Seismic Anisotropy in the Tibetan Plateau publication trend

The graph below shows the total number of articles in crustal dynamics and seismic anisotropy in the tibetan plateau across all publications each year (not limited to Nature Index journals).

Technical terms

Seismic anisotropy: Directional dependence of seismic wave speed caused by aligned minerals or structural fabrics in the Earth’s interior.

Crystal preferred orientation: Alignment of mineral grains during deformation, which imparts anisotropic seismic properties to rocks.

Rayleigh waves: Surface seismic waves that oscillate in an elliptical motion, sensitive to both crustal and upper-mantle structure.

Lithospheric delamination: Detachment and sinking of dense lower lithosphere into the mantle, leading to isostatic uplift of the overlying crust.

Big mantle wedge: A broad region of upwelling asthenosphere beneath a stagnant slab, characterised by low seismic velocities and enhanced seismic anisotropy.

References

1. Crystal preferred orientation of an amphibole experimentally deformed by simple shear. Nature Communications (2015).
2. Contemporary crustal movement of southeastern Tibet: Constraints from dense GPS measurements. Scientific Reports (2017).
3. Rayleigh-wave dispersion reveals crust-mantle decoupling beneath eastern Tibet. Scientific Reports (2015).
4. Massive lithospheric delamination in southeastern Tibet facilitating continental extrusion. National Science Review (2021).
5. The 3D Seismic Azimuthal Anisotropies and Velocities in the Eastern Tibetan Plateau Extracted by an Azimuth‐Dependent Dispersion Curve Inversion Method. Tectonics (2020).
6. Is there a big mantle wedge under eastern Tibet?. Physics of The Earth and Planetary Interiors (2019).