Seismic anisotropy in the mantle of a tectonically inverted extensional basin: A shear-wave splitting and mantle xenolith study on the western Carpathian-Pannonian region

Author(s)
Nóra Liptai, Zoltan Gráczer, Gyöngyvér Szanyi, Sierd A.P.L. Cloetingh, Bálint Süle, László Aradi, György Falus, Götz Bokelmann, Mate Timkó, Gábor Timár, Csaba Szabó, Kovacs Istvan, AlpArray Working Group
Abstract

Information on seismic anisotropy in the Earth's mantle can be obtained from (1) shear-wave splitting analyses which allow to distinguish single or multi-layered anisotropy and delay time of the fast and slow polarized wave can indicate its thickness, and (2) studying mantle peridotites where seismic properties can be inferred from lattice preferred orientation of deformed minerals. We provide a detailed shear-wave splitting map of the western part of the Carpathian-Pannonian region (CPR), an extensional basin recently experiencing tectonic inversion, using splitting data. We then compare the results with seismic properties reported from mantle xenoliths to characterize the depth, thickness, and regional differences of the anisotropic layer in the mantle. Mantle anisotropy is different in the northern and the central/southern part of the western CPR. In the northern part, the lack of azimuthal dependence of the fast split S-wave indicates a single anisotropic layer, which agrees with xenolith data from the Nógrád-Gömör volcanic field. Systematic azimuthal variations in several stations in the central areas point to multiple anisotropic layers, which may be explained by two distinct xenolith subgroups described in the Bakony-Balaton Highland. The shallower layer probably has a ‘fossilized’ lithospheric structure, representing former asthenospheric flow, whereas the deeper one reflects structures attributed to present-day convergent tectonics, also observed in the regional NW-SE fast S-wave orientations. In the Styrian Basin at the western rim of the CPR, results are ambiguous as shear-wave splitting data hint at the presence of multiple anisotropic layers. Spatial coherency analysis of the splitting parameters places the center of the anisotropic layer at ~140–150 km depth under the Western Carpathians, which implies a total thickness of ~220–240 km. Thicknesses estimated from seismic properties of xenoliths give lower values, pointing to heterogeneously distributed anisotropy or different orientation of the mineral deformation structures.

Organisation(s)
Department of Meteorology and Geophysics
External organisation(s)
Hungarian Academy of Sciences, Utrecht University, Hungarian Supervisory Authority for Regulatory Affairs, Eötvös Loránd University Budapest, Ungarisches Institut für Geschichtsforschung in Wien, Universität Wien
Journal
Tectonics
Volume
845
ISSN
0278-7407
DOI
https://doi.org/10.1016/j.tecto.2022.229643
Publication date
12-2022
Peer reviewed
Yes
Austrian Fields of Science 2012
105122 Seismic
Keywords
ASJC Scopus subject areas
Earth-Surface Processes, Geophysics
Portal url
https://ucris.univie.ac.at/portal/en/publications/seismic-anisotropy-in-the-mantle-of-a-tectonically-inverted-extensional-basin-a-shearwave-splitting-and-mantle-xenolith-study-on-the-western-carpathianpannonian-region(a85c3ab9-f253-4655-b3d4-8bb0e997806c).html