Probabilistic moment tensor inversion for hydrocarbon-induced seismicity in the groningen gas field, the netherlands, part 2: Application
by B. Dost (KNMI), A. Stiphout (Utrecht University), D. Kuehn (NORSAR en GFZ), M. Kortekaas (EBN), E. Ruigrok (KNMI)S. Heimann (GFZ)
Recent developments in the densification of the seismic network covering the Groningen gas field allow a more detailed study of the connection between induced seismicity and reactivated faults around the gas reservoir at 3 km depth. With the reduction of the average station distance from 20 km to 4–5 km, a probabilistic full-waveform moment tensor inversion procedure could be applied, resulting in both improved hypocenter location accuracy and full moment tensor solutions for events of M ≥ 2:0 recorded in the period 2016–2019. Hypocenter locations as output from the moment tensor inversion are compared to locations from the application of other methods and are found similar within 250 m distance. Moment tensor results show that the double-couple (DC) solutions are in accordance with the known structure, namely normal faulting along 50°–70° dipping faults. Comparison with reprocessed 3D seismic sections, extended to a depth of 6–7 km, demonstrate that (a) most events occur along faults with a small throw and (b) reactivated faults in the reservoir often continue downward in the Carboniferous underburden. From non-DC contributions, the isotropic (ISO) component is dominant and shows consistent negative values, which is expected in a compacting medium. There is some indication that events connected to faults with a large throw (> 70 m) exhibit the largest ISO component (40%–50%).
Dost, B., A. Stiphout, D. Kuehn, M. Kortekaas, E. Ruigrok and S. Heimann, Probabilistic moment tensor inversion for hydrocarbon-induced seismicity in the groningen gas field, the netherlands, part 2: Application