The Upper Silesian Coal Basin is the region where the great seismic activity is observed. The most
of seismic events have the energy not exceeding 107 J. Their localisation and character suggest the connections
with generation of new discontinuities in rock mass, induced by mining activity. The tremors
with higher energy are also registered but their frequency is much lower. In the time interval 1977—
1994 there were 3882 tremors with energy equal to 106 J or more occurring in the studied area, but
only 395 of them have energy not less than 107J. The flow of regional tectonic processes on origination
of the strongest seismic events is postulated by some authors investigating the induced seismicity of
the USCB.
The spatial distribution of tremor epicentres is not uniform in the USCB area. Despite of mining
activity carried out in all this area tremor epicentres concentrate in four regions connected with different
geological units. Inhomogenity of tremor spatial distribution suggests the fractal character of seismic
phenomena. The temporal variability of tremor epicentre co-ordinates shows some kind of “strange
attractors”. These facts could point that induced seismicity in the USCB is triggered by non-linear dynamical
process, having the regional meaning and connected with recent tectonic activity
