Mantle Structure in the Central Mediterranean Region From P and S Receiver Functions

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.

Multifrequency Inversion of Ps and Sp Receiver Functions: Methodology and Application to USArray Data

“…Their clear separation indicates that summing RFs from the entire data set would lead to averaging of lithospheric and upper mantle structure from different regions. Instead, it requires forming stacks that are sorted by back-azimuth (e.g., Vinnik et al, 2005;Vinnik et al, 2010;Monna et al, 2019).…”

“…Third, core phases (ScS, SKS, and their respective conversions) in the epicentral distance range ∼85° to 100° interfere with Sp conversions, in particular the S660p phase (X. Yuan et al, 2006). These issues can, however, to a large extent be mitigated through careful data selection and processing steps as described in, for example, Monna et al (2019); X. Shen et al (2019); and Wilson et al (2006).…”

“…Yuan et al, 2006). These issues can, however, to a large extent be mitigated through careful data selection and processing steps as described in, for example, Monna et al (2019); X. Shen et al (2019); and Wilson et al (2006).…”

“…The RF technique serves as an excellent tool to study lateral thermo-chemically induced variations in discontinuity structure (e.g. Kumar et al, 2005;Lawrence & Shearer, 2006;Sodoudi et al, 2006;Andrews & Deuss, 2008;Tauzin et al, 2008;Geissler et al, 2010;Vinnik et al, 2010;Cottaar & Deuss, 2016;Knapmeyer-Endrun et al, 2017;Tauzin et al, 2017;Makushkina et al, 2019;Monna et al, 2019;Munch et al, 2020).…”

“…The exact depth of these discontinuities (hereafter referred to as 410 and 660) is a nonlinear function of local temperature, pressure, and composition (Bina & Helffrich, 1994; Helffrich, 2000; Xu et al, 2008). The RF technique serves as an excellent tool to study lateral thermochemically induced variations in discontinuity structure (e.g., Andrews & Deuss, 2008; Cottaar & Deuss, 2016; Geissler et al, 2010; Kumar et al, 2005; Knapmeyer‐Endrun et al, 2017; Lawrence & Shearer, 2006; Makushkina et al, 2019; Monna et al, 2019; Munch et al, 2020; Sodoudi et al, 2006; Tauzin et al, 2008, 2017; Vinnik, 2010).…”