Hydrogeological effects of the latest Vogtland-NW Bohemian swarmquake period (August to December 2000)

Since 1989, hydrological, geochemical, and isotope investigations are accomplished at springs of the Upper Vogtland (Germany). The results give evidence of a fluidal response of the mineral spring `Wettinquelleʹ (formerly: `Radonquelleʹ) Bad Brambach to the seismogenic processes in the swarm quake area of Nov? Kostel (distance: 10 km), the most seismically active area in the region. In 1999, the measuring network was extended to groundwater drillings around the Wettinquelle, and multiparameter stations were installed at mofettes SW and S of the Nov? Kostel area. Beginning at the end of August 2000, the strongest swarmquake series compared with the 1985/86 swarms occurred in the area of Nov? Kostel. Hydrological and hydrochemical measurements show an anomalous behaviour of several parameters such as groundwater level, hydrostatic pressure, and free gas flow beginning at the end of July 2000, and partially, of a duration up to the first strong events of the autumn 2000 swarm. These precursor phenomena were the result of an increased fluidal pressure in the ground before the earthquakes. They were visible as higher static water levels in a gauge well and a stronger degassing of the mineral spring `Wettinquelleʹ. The anomalies confirm our co-seismic hydrogeological observations of the last 10 years at Bad Brambach, as well as our model conception of anomaly generation due to fluidal pressure pulses [Pure. Appl. Geophys. 157 (2000) 1621]. Furthermore, co- and post-seismic effects of hydrological and geoelectrical parameters were recorded in the mofette area of Soos and Bubl?k (Czech Republic).