Seismicity in the Upper Silesian Coal Basin, Poland: Strong regional seismic events

The Upper Silesian Regional Seismological Network (USRSN) installed in 1974, records all seismic events with 1.5 local magnitude, M-L greater than or equal to 1.5. In the USRSN data bank some fifty thousand seismic events have been collected. Thus relations between seismic events and mining work areas and geological structure can be studied. Seismic events can be divided into mining events low and moderate magnitudes M-L < 2.5; high seismic activity occurring at longwalls or openings, high rockburst hazard) and regional events (high magnitude 2.5 < M-L < 4.5; events occurring in fault areas and in flexural zones; high seismic hazard on the surface). In the generation of regional events not only lithostatic but also tectonic stresses play significant role. The largest regional events cause slight damage to many buildings of weak and moderate construction. Peak acceleration in the epicentral area versus seismic energy and peak acceleration versus distance are presented. A relationship between regional seismicity and local tectonics is also considered, and the examples of fault plane solutions for regional seismic events in the Upper Silesian Coal Basin are given.