SEISMICKÉ JEVY REGISTROVANÉ STANICÍ VRAC V ROCE 2017

Broadband seismic station VRAC, operated by Institute of Physics of the Earth (Masaryk University) and situated westwards of village Vranov u Brna, is equipped with seismometer STS-2 high gain and by digitizer Quanterra Q330. This instrumentation allows recording of broad band of frequencies from tenths of Hz to hundreds of seconds. It is important for usage of the VRAC station, which is part of several seismic networks, including Czech regional seismic network and global International Monitoring System of the CTBTO. In frame of these networks, station VRAC has to record of seismic signal of both local and teleseismic events. During year 2017, station VRAC recorded 6 855 seismic events (10 699 picked seismic phases). More than 70% of recorded events were represented by local events with epicentral distance less than 360 km. Induced events (mining tremors) and quarry blasts dominated among these local events. In addition, 197 natural tectonic events were recorded (89 on the territory of the Czech Republic). In the region of the Bohemian massif, most important natural seismicity was observed in the area of west Bohemia, where seismic swarm occured in July 2017. Exceptional tectonic event (10. 12. 2017, ML = 3.5) was recorded from the NE part of the Bohemian Massif (near Hlučín). About 25% of events registered by station VRAC were represented by teleseismic events with epicentral distance exceeding 2 000 km, including Korean nuclear test from 3. 9. 2017. Records of relatively small teleseismic events show signifi cant eff ect of the PKP caustic zone in respect of detectability of station VRAC.