Western U.S. seismic anisotropy revealing complex mantle dynamics

Mantle dynamics and seismic anisotropy

a r t i c l e i n f o Keywords: seismic anisotropy mantle flow geodynamic modeling shear wave splitting surface wave analysis mantle convection Observations of seismic anisotropy yield some of the most direct constraints available on both past and present-day deformation in the Earth's mantle. Insight into the character of mantle flow can also be gained from the geodynamical modeling of mantle ...

Depth dependent azimuthal anisotropy in the western US upper mantle

Seismic anisotropy: tracing plate dynamics in the mantle.

Elastic anisotropy is present where the speed of a seismic wave depends on its direction. In Earth's mantle, elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation. Earthquakes generate two seismic wave types: compressional (P) and shear (S) waves, whose coupling in anisotropic rocks leads to scattering, birefringence, and waves with hybr...

Superweak asthenosphere in light of upper mantle seismic anisotropy

Earth’s upper mantle includes a 200 km thick asthenosphere underneath the plates where viscosity and seismic velocities are reduced compared to the background. This zone of weakness matters for plate dynamics and may be required for the generation of plate tectonics itself. However, recent seismological and electromagnetic studies indicate strong heterogeneity in thinner layers underneath the p...

Seismic anisotropy in the lowermost mantle near the Perm Anomaly

The lower mantle is dominated by two large structures with anomalously low shear wave velocities, known as Large Low-Shear Velocity Provinces (LLSVPs). Several studies have documented evidence for strong seismic anisotropy at the base of the mantle near the edges of the African LLSVP. Recent work has identified a smaller structure with similar low-shear wave velocities beneath Eurasia, dubbed t...