Earthquake swarms in the Vogtland/Western Bohemia region: Spatial distribution and magnitude-frequency distribution as an indication of the genesis of swarms?

Vogtland/Western Bohemia is a small intraplate earthquake region in Central Europe covering about 6750 km2. A brief discussion of the geological background is followed by analysis of the recurrence of earthquakes affecting the area. Earthquakes are concentrated in a few zones. The location of earthquakes in two of them, the Markneukirchen/Plesná and the Nový Kostel zone, is discussed in detail. A special feature of the Vogtland/Western Bohemia seismicity is the clustering of earthquakes in time and space. The location of earthquakes within the cluster on December 1994 is shown. The effect of clustering is investigated in detail. A total of 73 clusters are characterized by their magnitude-frequency distribution, especially by the slope (b-value) of this distribution. In the plot of b-values versus the maximum magnitude of the cluster, the b-values are attracted by a few lines. Thus, clustering is regarded as a dynamic self-organized process. An existing model is improved by combining the existence of fluids and their post-seismic behaviour with the results of the earthquake clustering analysis.