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- Title
Surface‐Wave Tomography of the Central‐Western Mediterranean: New Insights Into the Liguro‐Provençal and Tyrrhenian Basins.
- Authors
Magrini, Fabrizio; Diaferia, Giovanni; El‐Sharkawy, Amr; Cammarano, Fabio; van der Meijde, Mark; Meier, Thomas; Boschi, Lapo
- Abstract
The complex tectonic setting of the central‐western Mediterranean has interested geoscientists for decades, but its geodynamic evolution remains a matter of debate. We rely on 807 seismometers from southern Europe and northern Africa to measure Rayleigh and Love phase velocities in the period range ∼5–200 s, based on teleseismic earthquakes and seismic ambient noise. By nonlinear joint inversion of the phase‐velocity maps, we obtain a 3‐D shear‐wave velocity (VS) model of the study area. At shallow depths, our model correlates with surface geology and reveals the presence of a sedimentary cover in the Liguro‐Provençal basin, as opposed to the Tyrrhenian basin where this is either very thin or absent. At ∼5‐km depth, high velocities below the Magnaghi, Vavilov, and Marsili seamounts point to an exhumed, scarcely serpentinized mantle. These are replaced by lower velocities at larger depths, likely connected to the presence of partial melt. At 50–60‐km depth, a very heterogeneous structure characterizes the Tyrrhenian basin, with low velocities pointing to the presence of fluids due to the lateral mantle inflow from the Ionian slab edges, and higher velocities associated with a relatively dry upper mantle. Such heterogeneity disappears at depths ≳75 km, replaced by more uniform velocities which are ∼2% lower than those found in the Liguro‐Provençal basin. We infer that, at the same depths, the Tyrrhenian basin is characterized by a larger concentration of fluids and possibly higher temperatures. Plain Language Summary: The Mediterranean area has long been considered by geoscientists as a source of inspiration for understanding geodynamic processes on a global scale, but its deep structure remains a matter of debate. We rely on seismic data from 807 receivers distributed across southern Europe and northern Africa to measure surface‐wave (Rayleigh and Love) phase velocities, based on both strong earthquakes and seismic ambient noise. We use these observables to obtain an improved shear‐velocity model of the central‐western Mediterranean, covering the Liguro‐Provençal and the Tyrrhenian basins. The shallow features of our model are consistent with known geological structures, and indicate a thick sedimentary cover in the Liguro‐Provençal basin which is absent beneath the Tyrrhenian Sea. At larger depths (∼50–60 km), we find a very heterogeneous structure in the Tyrrhenian basin, as opposed to the more uniform Liguro‐Provençal basin. The observation is consistent with a relatively high concentration of fluids in the south‐eastern part of the Tyrrhenian basin at the same depths, which can be ascribed to the subduction of the Ionian slab beneath Calabria. Our results are discussed in light of recent geodynamic models, with a focus on the role of slab dynamics in controlling the compositional character of back‐arc basins. Key Points: Rayleigh and Love phase‐velocity maps of the central‐western Mediterranean from seismic ambient noise and teleseismic earthquakesNew high‐resolution shear‐wave velocity model from joint inversion of Rayleigh and Love phase velocitiesVery heterogeneous structure in the Tyrrhenian basin at 50–60‐km depth associated with thermo‐chemical variations driven by slab dynamics
- Subjects
CALABRIA (Italy); AFRICA; BACK-arc basins; PHASE velocity; TOMOGRAPHY; TELECONNECTIONS (Climatology); MICROSEISMS; EARTH scientists; SEISMOMETERS
- Publication
Journal of Geophysical Research. Solid Earth, 2022, Vol 127, Issue 3, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB023267