Transversely isotropic lower crust of Variscan central Europe imaged by ambient noise tomography of the Bohemian Massif

0544673 - GFÚ 2022 RIV DE eng J - Journal Article
Kvapil, Jiří - Plomerová, Jaroslava - Kampfová Exnerová, Hana - Babuška, Vladislav - Hetényi, G.
Transversely isotropic lower crust of Variscan central Europe imaged by ambient noise tomography of the Bohemian Massif.
Solid Earth. Roč. 12, č. 5 (2021), s. 1051-1074. ISSN 1869-9510. E-ISSN 1869-9529
R&D Projects: GA ČR(CZ) GA21-25710S; GA MŠMT LM2010008; GA MŠMT(CZ) LM2015079; GA MŠMT(CZ) EF16_013/0001800
Institutional support: RVO:67985530
Keywords : surface wave tomography * upper mantle * Bohemian Massif
OECD category: Volcanology
Impact factor: 3.923, year: 2021
Method of publishing: Open access
https://se.copernicus.org/articles/12/1051/2021/

The recent development of ambient noise tomog-raphy, in combination with the increasing number of permanent seismic stations and dense networks of temporary stations operated during passive seismic experiments, provides a unique opportunity to build the first high-resolution 3-D shear wave velocity (upsilon(S)) model of the entire crust of the Bohemian Massif (BM). This paper provides a regional-scale model of velocity distribution in the BM crust. The velocity model with a cell size of 22 km is built using a conventional two-step inversion approach from Rayleigh wave group velocity dispersion curves measured at more than 400 stations. The shear velocities within the upper crust of the BM are similar to 0.2 km s(-1) higher than those in its surroundings. The highest crustal velocities appear in its southern part, the Moldanubian unit. The Cadomian part of the region has a thinner crust, whereas the crust assembled, or tectonically transformed in the Variscan period, is thicker. The sharp Moho discontinuity preserves traces of its dynamic development expressed in remnants of Variscan subductions im- printed in bands of crustal thickening. A significant feature of the presented model is the velocity-drop interface (VDI) modelled in the lower part of the crust. We explain this feature by the anisotropic fabric of the lower crust, which is characterised as vertical transverse isotropy with the low velocity being the symmetry axis. The VDI is often interrupted around the boundaries of the crustal units, usually above locally increased velocities in the lowermost crust. Due to the north-west-south-east shortening of the crust and the late-Variscan strike-slip movements along the north-east-south-west oriented sutures preserved in the BM lithosphere, the anisotropic fabric of the lower crust was partly or fully erased along the boundaries of original microplates.
Permanent Link: http://hdl.handle.net/11104/0321508