Beschreibung
The West Bohemia/Vogtland region on the German-Czech border is one of the most seismically active intracontinental regions in Europe. It is characterized by recurring earthquake swarms, degassing of mantle fluids at the surface, and magmatic processes in the lower crust and upper mantle. Numerous studies have shown that ascending fluids have an important role in triggering these swarms. However, to date, ascending zones of these fluids have only been identified in isolated areas through the crust, and the underlying processes of fluid-driven earthquake swarms have not yet been conclusively clarified. In order to identify these paths and analyze their interaction with seismic activity, we want to spatially image the attenuation structures and precisely determine the earthquake source parameters. The analysis of source spectra, seismic moments, corner frequencies, and spectral stress drops provide direct information about the physical conditions at the fault. Furthermore, the recording of local station amplifications enables the quantification of site-specific effects that significantly influence the modeling of ground motions. Furthermore, a new methodological approach will be developed that combines radiative transfer theory and attenuation tomography in an integrated process to consistently determine attenuation structures in high resolution. The aim of the project is to characterize seismic attenuation, the physical parameters of local earthquakes, and geodynamically relevant fluid migration in the West Bohemia/Vogtland region. Three work packages will be implemented: (1) Determination of nearsurface seismic attenuation using the spectral ratio method by comparing borehole and surface measurements, (2) Derivation of source spectra, seismic moments, corner frequencies, and spectral stress drops, even for low-magnitude earthquakes, using radiative transfer theory, and (3) performing t* tomography for 3-D imaging of the attenuation properties of the crust. The analysis is based on data of the seismic stations of the ICDP-Eger boreholes, permanent seismic networks, and the ELISE-Large-N network. The results are expected to include high-resolution images of seismic attenuation and site-specific amplifications, as well as detailed source parameters that contribute to the geodynamic interpretation of fluid-induced seismicity and provide the basis for improved seismic hazard assessment.