Spatial Distributions of the Induced Seismicity in the Upper Silesian Coal Basin

Abstract

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.