The possible transition of brittle failure to an aseismic process due to alteration of juvenile fluids in the NW-Bohemia/ Vogtland earthquake swarm region

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At the present state, the earthquake swarm activities at the NW-Bohemia/Vogtland region are interpreted as results of pore fluid pressure changes because the occurrence of earthquake swarms follow a diffusion-typical signature. We apply these results for our earthquake swarm trigger model but we prevent the explanation that these trigger effects of over-pressurized fluids are originated at magmatic reservoirs in the upper mantle. Our preliminary investigations suggest significant results that the necessary pore fluid pressure pluses are pressure transients from the surface which are induced by hydrological events (heavy rain, snowmelt). This pore pressure diffusion process from the uppermost groundwater reservoirs to the hypocenters needs several months according to the local hydraulic diffusivity of the interconnected conduits, the fault zones. Our preliminary results base on the analysis and correlation of two long term data sets: the continuously record of the Bad Brambach mineral spring discharge of about 30 years and the earthquake swarm activity of the Nový Kostel epicentral area at this period. The significant results give reason to the hypothesis that hydroseismicity can be considered as main trigger mechanism of the earthquake swarm activity at our area of investigation. The main goal of this project is to investigate and verify this hypothesis in detail, in particular for each epicentral cluster with their fault zones. Further, an investigation of additional pore pressure pulses along the shear zones due to the variations of the thermodynamic P-T-conditions during the rupture process will be considered as one specific target to understand the complete trigger processes. Besides the trigger processes, the approximation of the local earthquake swarm cycles will be used as a further important presumption to install a simplified long-term forecast system of the earthquake swarm activity for hazard reduction in that region.