Mantle Structure in the Central Mediterranean Region From P and S Receiver Functions. (29th October 2019)

• Record Type: Journal Article
• Authors: Monna, S.; Montuori, C.; Piromallo, C.; Vinnik, L.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 20:Number 10(2019)
• Page Start: 4545
• Page End: 4566
• Publication Date: 2019-10-29
• Subjects: receiver function -- nonlinear joint inversion -- Mediterranean -- Lehmann discontinuity -- mantle transition zone -- subduction; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2019GC008496
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: We investigate the upper mantle discontinuities in the central Mediterranean region by applying the P and S receiver function techniques on waveforms recorded at broadband stations located around the Tyrrhenian basin. P and S wave velocity profiles (down to 300‐km depth) are calculated with joint inversion of P and S receiver functions. We could identify the Moho, lithosphere‐asthenosphere boundary, and an underlying low‐velocity layer between ~60‐ and ~200‐km depth. The low‐velocity layer is interpreted as asthenospheric material, and its lower boundary is identified below the western Ionian and Tyrrhenian basins as a sharp Lehmann discontinuity. Although the stations are located on different lithospheric domains we find a strong correlation between Moho and the lithosphere‐asthenosphere boundary depths, which suggests ubiquitous coupling of the crust and lithospheric mantle, consistently with the southward opening of the Tyrrhenian basin. The Tyrrhenian and western Ionian basins present thinning of the transition zone of ~14 km, as inferred from a reduced P660s‐P410s differential time. Below the southern Apennines we observe a standard differential time that implies an average mantle transition zone thickness. We explain these mantle transition zone thickness variations as due to temperature heterogeneity linked to the area's subduction history. Finally, under central Europe (the location of the deep S ‐to‐ P conversion points) two strong signals from nonstandard discontinuities within the mantle transition zone are observed. These signals can be explained as being generated at the boundaries of high seismic velocity layers that are spatially correlated with stagnant slabs in the transition zone detected by seismic tomography. Plain Language Summary: The structure and composition of the Earth can lead to understanding its geological evolution. In this study, we use a method called the receiver function technique to understand the evolution of the central Mediterranean. This technique uses seismometer data to explore the interfaces (discontinuities) that separate the layers of the Earth. From shallowest to deepest, the discontinuities are the Moho, which separates crust and mantle, the lithosphere‐asthenosphere boundary, which separates the lithosphere and asthenosphere and the 410‐ and 660‐km discontinuities which together separate the upper and lower mantle. The discontinuities in the central Mediterranean area are particularly interesting. We found a strong correlation between the Moho and the lithosphere‐asthenosphere boundary depths throughout the Tyrrhenian region despite the fact that this area includes different tectonic plates. The finding suggests that a single mechanism controlled both crust and lithosphere thickness in this area during its evolution. At 400–600‐km depth, we found a thinning of the transition zone, which suggests that mantle temperatures are higher than the global average. Finally, we detected two discontinuities beneath central Europe, which testify to the existence of tectonic plates that sunk during past subduction (a process in which one plate moves under another) in the transition zone. Key Points: Joint inversion of P and S receiver functions constrains the lithosphere‐asthenosphere structure in the peri‐Tyrrhenian region A thin transition zone below the southern central Mediterranean suggests temperatures ~150°K higher than the global average Nonstandard discontinuities in the mantle transition zone below central Europe are associated with stagnant slabs