Ambient Noise Tomography Analysis in the Polish Sudetes: Preliminary results

During the last few years, the determination of the crust and upper mantle structures in southern Poland is the target of passive seismic experiments such as AniMaLS and PACASE. In this research, the area of Sudetes has been focused on that is located at the margin of the Bohemian Massif. This region 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 to the Quaternary. 

To provide information about the crust and upper mantle structure beneath the Sudetes region, Ambient Noise Tomography Analysis has been used. As the input, continuous seismic data acquired during about 2 years (2017 to 2019)   have been used. The acquisition involved 41 broadband seismic stations — 23 temporary stations deployed in the area of Sudetes and Fore-Sudetic block in SW Poland, supplemented with the data from 12 permanent seismic stations, operating in this area in the Czech Republic, Germany, and Poland. Furthermore, data from 6 broadband seismic stations of the Alp Array Seismic Network have been used. 

Ambient seismic noise methods are now well-established and used in different period bands for different scales. To retrieve the surface wave dispersion curves from the vertical component of recorded noise for a given station pair, the cross-correlation in the frequency domain and stacking of noise records has been done. Then, the spectra from every combination of station pairs are cross-correlated by selecting the longest common time window available between the two stations and the average inter-station dispersion measurements with respect to the periods that have been retrieved. In the next step, the Multiple Filter Analysis technique was applied to analyze the waveforms and obtain the group velocity dispersion curves. In the final step, we are working on surface wave tomography and applying inversion for the shear (or compressional) velocities in the region. Based on the preliminary results, the depth resolution is between 5-50 km and the average shear velocity that is calculated so far is about 2.8 to 4.5 km/s at these depths. 

 Financial support 

This presentation is supported by the National Science Centre, Poland, according to the agreements UMO-2019/35/B/ST10/01628 and UMO-2016/23/B/ST10/03204. 

Acknowledgments 

"The AniMaLS Working Group comprises: Monika Bociarska, Wojciech Czuba, Marek Grad, Tomasz Janik, Kuan-Yu Ke, Weronika Materkowska, Marcin Polkowski and Monika Wilde-Piórko."