Earthquake Triggered Modifications of Microtremor Signals above and nearby a Hydrocarbon Reservoir in Voitsdorf, Austria

We analyse the effects of an earthquake on the spectra of ground motion signals measured above and nearby a known oil and gas reservoir in the vicinity of Voitsdorf, Austria. The comparison of spectra of passive seismic data recorded before, during and after the earthquake indicates that a hydrocarbon reservoir can be stimulated by an earthquake. The stimulation results in an increase of power spectral density (PSD) in the low frequency range (around 3Hz) above the reservoir after the earthquake. An attribute quantifying the energy content of a spectrum, termed PSD-IZ, is increased after the earthquake above the reservoir. Also, the difference in the PSD-IZ values before and after the earthquake is largest above the reservoir. On the other hand, the ratio of the vertical to horizontal (V/H) spectral components of the ground motion signals is not sensitive to the earthquake.