Seismohydrological effects related to the NW Bohemia earthquake swarms of 2000 and 2008: Similarities and distinctions

Ulrich Koch , Jens Heinicke

For more than 20 years, seismo-hydrological investigations have been undertaken at the mineral aquifer system of Bad Brambach (Vogtland, Germany). Two strong swarm earthquake series in 2000-01 and 2008-09 at the Nový Kostel epicentre (Czech Republic, 10km E of BB) have enabled for the first time a comparison of seismological and groundwater hydraulic features in a semi-quantitative way. In spite of their similar spatial distribution in 2001 and 2008, the earthquake foci of each swarm migrated differently through time, horizontally as well as in depth. The seismic energy of the 2008-2009 events was released predominantly within one month, in contrast to 2000-2001 when it occurred over three months. The main distinctive features of each are seen in the hydraulic pressure anomalies which accompanied the earthquake swarms: number, shape, and progression (duration) of the anomalies. The comprehensive hydraulic data, with high temporal resolution, suggest that fluid triggering dominated not only the earthquake initiating phases. In particular, the long lasting seismicity of the 2008-2009 swarm can be attributed to a continued triggering of weak earthquakes by over-pressured deep fluids. Here, the remaining static strain was obviously not sufficient to generate strong earthquakes as at the beginning of the earthquake swarm periods. Furthermore, the enduring high fluid pressure in 2009 could also indicate a continuation of the long-term gas flow increase observed at several gas outlets in the Vogtland/NW Bohemia region between 1998 and 2008. However, it is not possible at present to derive a systematic relationship between anomaly occurrence and seismic activity, as generally proposed in the context of earthquake prediction discussion.

Mots clés: earthquake swarms; NW Bohemia; mineral water aquifer; hydrostatic pressure; groundwater level; anomaly comparison

Domaines: Sciences de la Terre

Ulrich Koch, Jens Heinicke. Seismohydrological effects related to the NW Bohemia earthquake swarms of 2000 and 2008: Similarities and distinctions. Journal of Geodynamics, 2010, 51 (1), pp.44. ⟨10.1016/j.jog.2010.07.002⟩. ⟨hal-00701270⟩