Possible role of fluids in the process of earthquake swarm generation in the West Bohemia/Vogtland seismoactive region

The West Bohemia/Vogtland region in the western part of the Bohemian Massif , known for periodic occurrence of earthquake swarms, is also characterised by 0.2-0.5 Ma old Quaternary volcanoes, rich CO2 emissions, anomalies of m antle-derived He, mineral springs and moffets. The detailed analysis of the time-space pattern of seismicity during the January 1997 swarm demonstrate s the gradual and ordered migration of rnicro-seismic activity, suggesting the step-by-step penetration of fluids into a small fractured volume. This scenario is supported by the similarity of the source mechanisms of the nat ural events of the January 1997 swarm with artificial injection-induced mic ro-earthquakes during the German deep drilling project (KTB) in neighbourin g NE Bavaria. Also the comparison of the West Bohemia/Vogtland earthquake s warm region with other intraplate earthquake swarm regions and with earthqu ake swarms induced by current volcanic processes indicates a role of intrus ions of magma and related fluids in generation process of earthquake swarms . (C) 2001 Elsevier Science B.V. All rights reserved.