Seismic anisotropy, observed in the lowermost mantle near Large Low-Shear-Velocity Provinces (LLSVPs), is likely caused by strong deformation from mantle flow interacting with these regions or plume formation. This study explores slab-induced plume generation from thermochemical piles (LLSVPs) and resulting flow behavior using 3-D regional-scale mantle convection models in ASPECT, coupled with mantle fabric simulations in ECOMAN. Various models with different LLSVP density and viscosity were tested. The modeling of the lattice preferred orientation with predominant activity of the slip system [001](100) for Bridgmanite and [100](001) for post-Perovskite reveals that the lower mantle is generally isotropic, except (i) in regions of plume conduits where vertically polarized shear waves (Vsv) are faster, and (ii) in the lowermost mantle characterized by fast horizontally polarized shear waves (Vsh) that transition to fast Vsv at the margins of the rheologically stiffer LLSVP piles where deformation and upwelling of the surrounding mantle take place.

Seismic anisotropy is key to constrain mantle flow, but it is challenging to image and interpret it. To better understand the robustness of anisotropy tomography, we create a 2-D ridge-to-slab geodynamic model and compute the associated fabrics. Using the resulting 21 elastic constants we compute seismic waveforms, which are inverted for isotropic and radially anisotropic structure. We test the effects of different data coverage and levels of regularisation on the resulting images and on their geodynamical interpretation. The retrieved isotropic images exhibit substantial artificial slab thickening and loss of the slab’s high velocity signature below ~100 km depth. Our results also show that regularisation and data coverage strongly control the characteristics of the retrieved depth-age dependency of anisotropy, leading to an artificial flat depth-age trend shown in existing anisotropy tomography models. Greater data coverage and additional complementary data types are needed to improve the resolution of (an)isotropic tomography models.

We present the first 3D anisotropic teleseismic P-wave tomography model of the upper mantle covering the entire Central Mediterranean. Compared to isotropic tomography, we find that including the magnitude, azimuth, and, importantly, dip of seismic anisotropy in our inversions simplifies isotropic heterogeneity by reducing the magnitude of slow anomalies while yielding anisotropy patterns that are consistent with regional tectonics. The isotropic component of our preferred tomography model is dominated by numerous fast anomalies associated with retreating, stagnant, and detached slab segments. We also observe relatively slower mantle structure related to slab windows and the opening of back-arc basins. To better understand the complexities in slab geometry and their relationship to surface geological phenomenon, we present a 3D reconstruction of the main Central Mediterranean slabs down to 700 km based on our anisotropic model. P-wave seismic anisotropy is widespread in the Central Mediterranean upper mantle and is strongest at 200-300 km depth. We interpret the anisotropy patterns as the result of asthenospheric material flowing primarily horizontally around the main slabs in response to pressure exerted by their mid-to-late Cenezoic horizontal motion. We also image sub-vertical anisotropy possibly reflecting asthenospheric entrainment by descending lithosphere. Our results highlight the importance of anisotropic P-wave imaging for better constraining regional upper mantle geodynamics.