Discrimination between local earthquakes and quarry blasts in the Vértes Mountains, Hungary

We present our analysis of the characteristics of the waveforms of earthquakes and quarry blasts that occurred within extreme local-distance (< 25 km) of Csokakő (CSKK) station in the Vertes Hills, Hungary. Our motivation was to determine the linear discrimination line between the earthquake and explosion populations. CSKK is located in the Mor Graben, a seismically relatively active region, and also characterized by significant mining activity. Contamination of earthquake catalogues with anthropogenic events largely complicates seismotectonic interpretation. It is especially true for relatively low seismicity areas, such as Hungary where more than 50% of the recorded seismicity is attributed to anthropogenic events. We tested the effectiveness of the maximum P/S amplitude ratios in various frequency bands. Because most of the quarry blasts are carried out by ripple-fire technology, we also computed spectrograms and examined the spectral ratio between low and high frequencies and the steepness of spectra. We found that earthquakes and quarry blasts are best separated by the linear discrimination that combines the amplitude ratios and the different spectral ratios.