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Abstract:
Located in the northern part of the Netherlands, the Groningen gas field is one of the largest gas fields in Europe and is known as an earthquake-prone area for induced seismicity. The prolonged gas extraction in the area have been pointed out as the main cause of the earthquakes. While many studies have indicated that the earthquakes mainly originated from the reservoir layer, several latest studies show the possibility that the majority of the earthquakes nucleated just above the reservoir layers. In this study, we investigate the possibility of the latter hypothesis as well as the main mechanisms of the Groningen earthquakes. To do that, we applied an efficient probabilistic algorithm, the Hamiltonian Monte Carlo algorithm. The aim is to estimate ten earthquake source parameters. Those are the moment tensor (six components), hypocenter (three coordinate components), and origin time. Having the probabilistic estimates of the parameters, we then compare them with the reservoir map of Groningen to asses the pre-described hypothesis. We also used the fault map of the Groningen subsurface to see the match between the mechanisms we obtained and the orientation of the mapped subsurface faults. Additionally, we also compare our results with several related research from the area. In the end, we found that there is indeed a high probability of earthquakes nucleated just above the reservoir level, with the mechanisms mainly triggered by the movement of the mapped subsurface faults.
