Intra-continental earthquake swarms in West-Bohemia and Vogtland: A review

Earthquake swarms and high CO2 flow of mantle origin are the characteristic features of West Bohemia/Vogtland (Central Europe). At present, the highest concentration of earthquake activity and CO2 degassing occurs in the area of the Cheb Basin at the intersection of the Eger Rift and Regensburg–Leipzig–Rostock Zone with three Quaternary active volcanoes. We review about 140 studies on structure, tectonics, volcanism, seismicity, earthquake source, triggering mechanisms, and gas-isotope geochemistry focused on the earthquake swarms from this area with the aim to build a complex image of the ongoing processes and find a possible link between activity of the mantle-derived fluids and the earthquake swarms. The so far unpublished data on the 2011 swarm and little known data on the 1824 swarm are presented, as well, showing that earthquake swarms activate a complex fault system and display long-term migration that differs from the occurrence of CO2 escapes. The activity of individual swarms is consistent with models involving high-pressure fluids; the isotopic signature of the rising gas proves its origin at depths below the hypocenters. We show that the earthquake swarms and degassing of CO2 of magmatic origin represent common result of the geodynamic activity of the area. Nevertheless, current knowledge does not preclude processes other than fluid-induced failure in triggering swarm seismicity.