Analysis of the Epicenter Location Accuracy for the Local Seismic Network Operated in the Mining Area Towards the Automation of Location Procedures

Abstract

Legnica-Głogów Copper District (LGCD) is one of the most active seismic regions in Europe. Several thousand seismic events induced by underground copper mines are recorded there each year, with the strongest reaching magnitudes above 4. Seismicity in LGCD is monitored by the LUMINEOS surface seismic network and the mine's underground networks. While the horizontal location uncertainty of the LUMINEOS network is about 300–600 m, the declared epicenter uncertainty of dense mine networks is less than 50 m. It gives us a unique opportunity to test the location accuracy of seismic events recorded by the LUMINEOS network determined with various algorithms and automatic procedure. In our work, we compared the location accuracies of traveltime-based algorithms LocSAT and NonLinLoc as well as waveform-based algorithm BackTrackBB. The iterative, Geiger-type LocSAT algorithm is used in routine daily processing for the LUMINEOS. Its downside is the need to use the S wave onset times, which in the case of the LUMINEOS network are very uncertain. As an alternative, we tested the probabilistic NonLinLoc algorithm, and the waveform based BackTrackBB algorithm. The BackTrackBB algorithm is known to work well with local, high noise seismic networks. We aimed to find out if it could be used routinely with the LUMINEOS data. In addition, we conducted a comparative analysis of the location uncertainty of these algorithms to determine the effectiveness of this parameter in assessing accuracy.