On the aftershock productivity in mining-induced seismicity-insight into seismicity of Rudna copper ore mine, Poland

Mining-induced seismic events can be followed by aftershocks that increase the risk associated with the exploitation. The understanding of the aftershock generation process in induced seismicity may improve post-earthquake safety procedures applied in mines. Rudna copper ore mine in southwestern Poland commonly experiences intense and strong seismic activity accompanying the room-and-pillar exploitation of copper ore. Some strong (magnitude >2) mining events are followed by numerous aftershocks and some are not followed by any. In this study, we seek to find whether there is any geological, technological or seismological cause of this diversity. We study 46 strong mining events and focus on their aftershock productivity. We analyse the geological and mining setting of the studied events, their signal similarity, stress drops and the ground motion effect using data from three different seismic networks. Our results show that seismic events producing large aftershock sequences may share similar focal mechanisms and have larger ground effects than events with no aftershocks. The results also indicate the potential differences in stress drops. This interesting observation may help to better evaluate the aftershock hazard in mines. It also indicates the need for a more detailed analysis of the focal mechanisms of strong events and their relationship to the exploitation technique.