Magnitudes and time distribution of the swarm earthquakes August–November 2000 in NW Bohemia

During the earthquake swarm in the north-western part of the Czech Republic which happened between August and November 2000 more than 10 500 single events have been recorded at the station Wernitzgruen (WERN), located in the Vogtland (Germany) at about 13 km hypocentral distance. Most of the events were weak and followed each other so closely in time that they could not be identified at more distant stations in Middle Europe. A procedure to determine magnitudes of very small events from recordings in short distances is realized and discussed. The development over time of the seismic activity shows the typical pattern of previous earthquake swarms in this region consisting of multiple swarm episodes. For the first time, however, it is analysed using the time intervals between successive events. However, no new and reproducible patterns were found which could be useful for prognostics of future swarm activities.