Mining-Induced Seismicity in the Saarland, Germany

Abstract

Coal mining in the Saar mine, Germany, is accompanied by mining-induced seismic events. Strong events occur only in certain areas of the mine, other areas exhibit almost no seismicity. Shear events occur simultaneously to non-shear events. The shear events occur in different depths but their epicenters do concentrate in bands. The strike of the bands coincides with the strike of larger regional faults in the area. The seismic events of the Saar mine show some characteristics which distinguish them from seismic events observed in other German coalfields. The Gutenberg–Richter relation, for example, does not hold for these events. Furthermore, radiated seismic energy and extracted coal volume are not correlated. In the Primsmulde field a strong seismic event was observed even before mining in that region started. The event was triggered just by driving roadways into the field. The shear events cannot be explained by the mining process alone. They are presumably induced in certain regions (bands) under tectonic load by an interaction of mining-induced and tectonic stresses. In February 2008, extraction in the Primsmulde field induced a seismic event of magnitude 4, which led to surface vibrations reaching 93 mm/s. After this event, the Primsmulde field had to be abandoned. Future extraction of the Saar mine will be restricted to some small areas not intersected by the event bands found in the Dilsburg Ost and Primsmulde fields. The Saar mine will close in 2011.