The PASSEQ Working Group: Wilde-Piórko M., Geissler W.H., Plomerová J., Grad M., Babuška V., Brückl E., Cyziene J., Czuba W., England R., Gaczyński E., Gazdova R., Gregersen S., Guterch A., Hanka W., Hegedűs E., Heuer B., Jedlička P., Lazauskiene J., Keller G.R., Kind R., Klinge K., Kolinsky P., Komminaho K., Kozlovskaya E., Krüger F., Larsen T., Majdański M., Malek J., Motuza G., Novotný O., Pietrasiak R., Plenefisch T., Růžek B., Sliaupa S., Środa P., Świeczak M., Tiira T., Voss P., Wiejacz P.

We present a high-resolution study of the upper mantle structure of Central Europe, including the western part of the East European Platform, based on S-receiver functions of 345 stations. A distinct contrast is found between Phanerozoic Europe and the East European Craton across the Trans-European Suture Zone. To the west, a pronounced velocity reduction with depth interpreted as lithosphere–asthenosphere boundary (LAB) is found at an average depth of 90 km. Beneath the craton, no strong and continuous LAB conversion is observed. Instead we find a distinct velocity reduction within the lithosphere, at 80–120 km depth. This mid-lithospheric discontinuity (MLD) is attributed to a compositional boundary between depleted and more fertile lithosphere created by late Proterozoic metasomatism. A potential LAB phase beneath the craton is very weak and varies in depth between 180 and 250 km, consistent with a reduced velocity contrast between the lower lithosphere and the asthenosphere. Within the Trans-European Suture Zone, lithospheric structure is characterized by strong heterogeneity. A dipping or step-wise increase to LAB depth of 150 km is imaged from Phanerozoic Europe to 20–22° E, whereas no direct connection to the cratonic LAB or MLD to the east is apparent. At larger depths, a positive conversion associated with the lower boundary of the asthenosphere is imaged at 210–250 km depth beneath Phanerozoic Europe, continuing down to 300 km depth beneath the craton. Conversions from both 410 km and 660 km discontinuities are found at their nominal depth beneath Phanerozoic Europe, and the discontinuity at 410 km depth can also be traced into the craton. A potential negative conversion on top of the 410 km discontinuity found in migrated images is analyzed by modeling and attributed to interference with other converted phases.