A High‐Resolution Shear Velocity Model of the Crust and Uppermost Mantle Beneath Westernmost Mediterranean Including Radial Anisotropy

Abstract

Using seismic data from 1,186 stations deployed across the westernmost Mediterranean, we construct a high‐resolution 3‐D radially anisotropic model from a joint inversion of receiver functions and Rayleigh and Love wave dispersions. The Rayleigh and Love data are extracted from both ambient noise interferograms and earthquake waveforms, and a new three‐station ambient noise interferometry method is used to further improve the data coverage. The obtained crustal thickness map reproduces independently the Moho depth maps compiled from previous data, showing crustal roots beneath the Pyrenean‐Cantabrian range and the Gibraltar Arc and thicker crust beneath the Variscan Iberian Massif than in the area affected by Alpine orogenesis. The Vsv crustal model outlines the Iberian Massif as a high shear wave velocity block and shows extremely low velocities in the Gulf of Cadiz and Gibraltar Arc. At mantle levels, a sharp boundary between the Aquitanean Basin and the Massif Central is imaged, with low Vsv beneath the Massif Central probably reflecting a remaining signature of the magma. To the south of Iberia, the geometry of the Alboran slab is captured by the model, while beneath the Atlas Mountains, widespread low Vsv and positive radial anisotropy is observed, favoring the edge‐driven convection model explaining the lithospheric thinning. The most relevant contribution of this work is mapping, for the first time at this scale, the radial anisotropy anomalies at crustal level, with higher values observed in the Alpine Iberia, dominated by present‐day extensional tectonics.

Mega‐Folding of a Basement During Incipient Intra‐Plate Continental Subduction (Alpine Central Iberia)

“…Nevertheless, the map does not have adequate resolution to detect crustal folds with a wavelength of a few tens of km as the one here deduced. Recently, a shear velocity model of the crust and uppermost mantle has been developed for Iberia (Feng & Diaz, 2023). In the study area, the V sv crustal model outlines an open antiform visible in the 3 and 10 km depth maps (Figures 5a and 5b), also observed in crosssection (Figure 5c), with higher V sv in the SPCS close to the surface than in the surrounding areas.…”

Crustal Structures From Receiver Functions and Gravity Modeling in Central Mongolia

“…We decided to look only for layer thickness, V p, V s, dip, and strike within the crust. Even if methods allow to investigate the anisotropic behavior of crustal part (Feng, 2021; Feng & Diaz, 2023; Shen et al., 2013), the anisotropy is too complex in our multilayer model to be constrained. Besides, we are looking for intracrustal information we can combine with gravity signal, and anisotropy will be of no help in our case.…”