Rotational ground motion recordings in the West Bohemia / Vogtland region for waveform inversion for seismic moment tensors

In synthetic tests, rotational ground motion recordings proved to be beneficial for the wavefrom inversion for seismic moment tensors. In a next step, we want to verify these findings using real measurements. To do so, we installed two broadband rotational collocated to translational ground motion sensors in the West Bohemia / Vogtland area in summer 2022.

The area is characterised by regular seismic swarm activity, the last one occurring in December 2021. The seismic swarms are known to be connected with crustal flow of mantle fluids. However, the detailed mechanism of this connection is not well understood yet. Full seismic moment tensors, especially their non-double-couple part, will contribute to investigate the connection between swarm activity and fluid flow. So far, a lacking number of moment tensors and difficulties in the reliability of the non-double-couple part hampered the analysis in the study area. Including rotational ground motion recordings to waveform inversion will help to overcome these difficulties.

In seven months, we have recorded 120 events with magnitudes larger than M ≥ 0 in a distance of up to 35 km, thereof 35 around Nový Kostel, the center of the swarm activity. Considering that rotational sensors are about 2-4 times less sensitive than translational sensors (depending on the local phase velocity of the location) this is already a great success. Here, we show details of the sensor installations, first data analysis, and an estimate on the magnitude of completeness from rotational measurements.