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The West-Bohemian/Vogtland region (Germany/Czech Republic) is well known for its frequent intraplate swarm activity related to fluid flow within the crust. Previous studies found that non-double-couple components (non-DC: isotropic, CLVD) contribute significantly to the seismic moment tensors of these events. They were interpreted as tensile faulting associated with the migration of deep magmatic fluids through the crust. However, so far the results are restricted to a few larger events. The accurate and precise determination of non-DC components during waveform inversion for moment tensors is difficult, especially for smaller magnitude events (MIn earlier synthetic studies the joint inversion of translational and rotational waveforms improved the resolution of the moment tensor. In this project “NonDC-BoVo” – funded within the frame of the ICDP EGER project – two rotational sensors were deployed collocated with translational seismometers. The acquired data present one of the first examples using field data to invert waveforms for the moment tensor. The sensors show a good sensitivity even for low magnitude events. In seven months, the “Seismologie-Verbund zur Erdbebenbeobachtung in Mitteldeutschland” reports 521 events occurring within a distance of up to 30 km.Here, we present data examples together with an estimation of the magnitude of completeness from rotational recordings. Based on the signal-noise-ratio, we estimate a magnitude of completeness of around 0.3 for the rotational data compared to -0.7 from the catalogue. We found that the transversal translation corresponds well to the vertical rotation for a phase velocity of 2000 m/s at frequencies of 10-20 Hz., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

We present first data examples and an estimation of the magnitude of completeness for two BlueSeis-3A rotational seismometers deployed in the West-Bohemia/Vogtland region. The sensors show a surprisingly good sensitivity even for low magnitude events. In seven months, the "Seismologie-Verbund zur Erdbebenbeobachtung in Mitteldeutschland" reported 521 events occurring within a distance of up to 30 km. Based on the signal-noise-ratio, we estimate a magnitude of completeness around a local magnitude of 0.3 for the rotational sensors compared to the completeness of the catalog of -0.7. Moreover, we found that the transversal translation corresponds well to the vertical rotational component for a phase velocity of 2000 m/s and frequencies of 10 to 20 Hz. The data are intended to complement waveform inversions for seismic moment tensors. The study area is characterized by recurring seismic swarms, which are presumably driven by the migration of mantle fluids through the crust. In order to better understand the role of fluids in the earthquake mechanim a good resolution of the non-double-couple (i.e. volumetric and tensile) components of the seismic moment tensor is needed. In that regard, adding rotational data to the inversion has been shown beneficial in synthetic studies. The acquired data will present one of the first examples using field data to invert waveforms for the full seismic moment tensor., poster

Even though micropolar theories are widely applied for engineering applications such as the design of metamaterials, applications in the study of the Earth’s interior still remain limited and in particular in seismology. This is due to the lack of understanding of the required elastic material parameters present in the theory as well as the eigenfrequency $\omega _r$ which is not observed in seismic data. By showing that the general dynamic equations of the Timoshenko’s beam is a particular case of the micropolar theory we are able to connect micropolar elastic parameters to physically measurable quantities. We then present an alternative micropolar model that, based on the same physical basis as the original model, circumvents the problem of the original eigenfrequency $\omega _r$ laking in seismological data. We finally validate our model with a seismic experiment and show it is relevant to explain observed seismic dispersion curves., Westfälische Wilhelms-Universität Münster (1056)

Reducing wind turbine noise recorded at seismological stations promises to lower the conflict between renewable energy producers and seismologists. Seismic noise generated by the movement of wind turbines has been shown to travel large distances, affecting seismological stations used for seismic monitoring and/or the detection of seismic events. In this study, we use advanced 3D numerical techniques to study the possibility of using structural changes in the ground on the wave path between the wind turbine and the seismic station in order to reduce or mitigate the noise generated by the wind turbine. Testing a range of structural changes around the foundation of the wind turbine, such as open and filled cavities, we show that we are able to considerably reduce the seismic noise recorded by placing empty circular trenches approx. 10 m away from the wind turbines. We show the expected effects of filling the trenches with water. In addition, we study how relatively simple topographic elevations influence the propagation of the seismic energy generated by wind turbines and find that topography does help to reduce wind-turbine-induced seismic noise., Finanziert durch den Open-Access-Publikationsfonds der Westfälischen Wilhelms-Universität Münster (WWU Münster).