Aftershock productivity in mining-induced seismicity ‑ the case of Rudna copper ore mine, Poland.

Abstract:

The phenomenon of aftershocks is known both in natural and induced seismicity (IS). Aftershocks observed during exploitation of natural resources may increase the risk associated with the process. It is particularly important in the case of mining, where they pose an extra hazard to people working underground and infrastructure. The earthquakes generation process in induced seismicity has been deeply studied, especially in the last decade. However, so far there was no much effort put particularly in the understanding of IS aftershocks. Such knowledge would be the key to improving the post-earthquake safety procedures applied e.g. in mines. Rudna copper ore mine in southwestern Poland is a good example of the production causing a serious induced seismicity problem. The room-and-pillar type exploitation is accompanied by intense seismicity where some strong (magnitude >2) events are followed by numerous aftershocks and some are not followed by any. In this study we use the extensive dataset from three networks to find whether there is any geological, technological or seismological difference between seismic events with high and low aftershock productivity. We study 46 strong mining events and analyze their geological and mining setting, signal similarity, stress drops and ground motion effect. We find that aftershock-productive seismic events may share similar focal mechanism, have higher stress drops and larger ground effect than events with no aftershocks. Such findings may improve both post-earthquakes procedures and ground motion prediction.