Chatseis data acquisition: Combination of seismic reflection imaging and full-waveform inversion for glacial overdeepened valleys

The DFG-funded project Chatseis (BU3894/3-1, KO6375/2-1) intends to combine high-resolution seismic reflection imaging and full waveform inversion (FWI) for better understanding of overdeepened valleys. By combining both methods, we expect an improvement in resolution, accuracy, and reliability of the data analysis. To develop our workflow and answer scientific questions regarding the ICDP project Drilling Overdeepened Alpine Valleys, we record seismic datasets at ICDP sites 5068_3 (Schäftlarn, GER) and 5068_5 (Bad Aussee, AUT).

At Schäftlarn, about 30 km south of the city of Munich, we acquired three high-resolution P-wave profiles with various receivers (Burschil, 2024). Seismic sources are the 4 t hydraulic vertical mini-vibrator MHV4P, vertical and horizontal wheelbarrow-size ELVIS vibrators, and 26 explosions of 1 kg, conducted by the LfU.

Preliminary results show the structure of the valley, which are in accordance with the interpretation of the ICDP drill core. Reflections from the valley base are caused by the strong impedance contrasts of Quaternary sediments and Molasse bedrock. Basin internal reflections mark the boundary between gravels and glacial sediments. A first arrival traveltime tomography (FATT) of the explosive source data was performed as preparation for the FWI. The FATT velocity distribution shows high velocities for the gravel units and decreasing velocity towards north. Reflection image and velocity distribution are in good agreement.

The seismic campaign at Bad Aussee is scheduled for June 2024.

Burschil 2024. Seismic measurements, Project Chatseis. BGR Survey report. doi:10.25928/pet1-6838