Abstract
Abstract. We present high-resolution tomographic images of the upper mantle beneath the Eastern Alps and the adjacent Bohemian Massif (BM) in the north based on recordings from the AlpArray-EASI and AlpArray seismic networks. The tomography locates the Alpine high-velocity perturbations between the Periadriatic Lineament and the Northern Alpine Front. The northward-dipping lithosphere is imaged down to ∼ 200–250 km of depth, without signs of delamination. The small amount of crustal shortening compared to that in the Western Alps and the bimodal character of the positive perturbations with a separation beneath the Tauern Window indicate a dual source of the velocity heterogeneity, most probably formed by a mixture of a fragment of detached European plate and the Adriatic plate subductions. A detached high-velocity heterogeneity, sub-parallel to and distinct from the Eastern Alps heterogeneity, is imaged at ∼ 100–200 km beneath the southern part of the BM. We associate this anomaly with the western end of a SW–NE-striking heterogeneity beneath the south-eastern part of the BM, imaged in models of larger extent. The strike, parallel with the Moldanubian–Brunovistulian mantle–lithosphere boundary in the BM and with the westernmost part of the Carpathian front, leads us to consider potential scenarios relating the heterogeneity to (1) a remnant of the delaminated European plate, (2) a piece of continental-and-oceanic lithosphere mixture related to the building of the BM, particularly to the closure of the old Rheic ocean during the MD–BV collision, or (3) a lithospheric fragment going through to the NW between the Eastern Alps and Western Carpathians fronts in a preceding subduction phase. The study is dedicated to our outstanding and respected colleague Vladislav Babuška, who coined innovative views on the European lithosphere and died on 30 March 2021.
Highlights
Teleseismic body-wave tomography represents a powerful tool to study regional velocity structure of the upper mantle and to image velocity anomalies, those related to subducted plates in collision zones
The distinct, high-velocity, northward-dipping, ∼ 140 km broad perturbations related to the eastern Alpine root, imaged in the upper ∼ 250 km of the mantle by previous tomography (Babuška et al, 1990; Karousová et al, 2013; Hetényi et al, 2018b), had a tendency to split when we exploited data from the EASI experiment and nearby permanent stations (Plomerová et al, 2018)
“only” adding data from the AASN led to the clear visualization of two separate sub-parallel high-velocity heterogeneities beneath the broader eastern Alpine region, both dipping to the north and each about 80 km thick (Figs. 2 and 3), with a low-velocity separation zone of ∼ 80–100 km extent
Summary
Teleseismic body-wave tomography represents a powerful tool to study regional velocity structure of the upper mantle and to image velocity anomalies, those related to subducted plates in collision zones. J. Plomerová et al.: Two subduction-related heterogeneities beneath the Eastern Alps models of segmented Alpine slab during the last decades (Wortel and Spakman, 2000; Kissling et al, 2006; Malusa et al, 2021, for reviews). The density of stations and teleseismic rays enabled resolving the highvelocity heterogeneities only on a 1.5◦ × 1.5◦ grid, but the bent shape of the south-eastward-dipping subduction of the European plate in the Western Alps and steep northwarddipping lithosphere beneath the Eastern Alps, with a gap between the two Alpine slabs, were evident. More recent tomographic studies from data recorded in regional passive seismic experiments with densely spaced stations re-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
