<p>The area of Sudetes, located at the margin of the Bohemian Massif, represents the NE-most part of the Variscan internides between the Elbe Fault in SW and the Odra Fault in NE. The lithosphere of the region is a mosaic of several distinct units/terranes with complex tectonic history ranging from the upper Proterozoic till the Quaternary. The crustal and uppermost mantle structure of this region was studied by seismic wide-angle experiment SUDETES 2003 and the results of 2-D isotropic modelling were published. Recently, this dataset, comprising off-line recordings from a net of intersecting profiles, was interpreted using anisotropic delay-time inversion. This resulted in models of 2-D distribution of upper crustal and uppermost mantle anisotropy based on azimuthal variability of the Pg and Pn traveltimes, respectively. The upper mantle of Sudetic region was the target of a passive seismic experiment AniMaLS. The project involved 23 broadband seismic stations deployed in the area of Sudetes and Fore-Sudetic block in SW Poland, supplemented with the data from 6 permanent seismic stations, operating in this area in Czech Republic and Poland. The measurements cover a ~200x100 km large area, with ~30 km inter-station spacing. The stations, deployed for a period of 24 months (2017-2019), provided broadband recordings of local, regional and teleseismic events. The aim of the experiment is to study the structure, seismic velocity variations including anisotropy distribution, and to map the upper mantle seismic discontinuities (Moho, lithosphere-asthenosphere boundary, mantle transition zone). Currently, the AniMaLS data are being interpreted using shear wave splitting method and receiver function method. The analysis of SKS and SKKS splitting was based on cross-correlation, eigenvalue minimization and transverse energy minimization methods. Resulting time delays between slow and fast S-wave components are ~1.2 sec on average, with fast velocity axis oriented largely in WNW-ESE direction, consistently with results of delay-time inversion of Pn phase traveltimes. Crustal anisotropy is characterized by similar fast axis orientation, but with lower amplitude of anisotropy. The orientation of fast axes in the crust and mantle correlates well with surface trends of tectonic units and with strike directions of major fault zones. This suggests vertically coherent deformation throughout the lithosphere, most likely during consolidation of the Sudetic region in Variscan times.</p>
Abstract. The paper presents information about the seismic experiment “AniMaLS” which aims to provide a new insight into the crust and upper mantle structure beneath the Polish Sudetes (NE margin of the Variscan orogen). The seismic network composed of 23 temporary broadband stations was operated continuously for about 2 years (October 2017 to October 2019). The dataset was complemented by records from eight permanent stations located in the study area and in the vicinity. The stations were deployed with an inter-station spacing of approximately 25–30 km. As a result, recordings of local, regional and teleseismic events were obtained. We describe the aims and motivation of the project, the station deployment procedure, as well as the characteristics of the temporary seismic network and of the permanent stations. Furthermore, this paper includes a description of important issues like data transmission setup, status monitoring systems, data quality control, near-surface geological structure beneath stations and related site effects, etc. Special attention was paid to verification of correct orientation of the sensors. The obtained dataset will be analysed using several seismic interpretation methods, including analysis of seismic anisotropy parameters, with the objective of extending knowledge about the lithospheric and sublithospheric structure and the tectonic evolution of the study area.
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