Seismic activity and occurrence of mineral waters are observed in the Hronov-Porici fault area. Local seismicity
effects on groundwater sources were observed in connection with strong 1901 north-eastern Bohemia
earthquake, but the systematic observation started only in 2005. Due to installation of OST small-aperture array
operating since that year, very weak microearthquakes from M > -2 are registered and localized. This weak
seismic activity has swarm-like character. Four hypocentral zones were found. The former project was aimed at
determination of local seismicity effects on groundwater level. Because a promising correlation of water level
changes with seismic activity was found in case of several events and longer time series of data are needed,
current project will continue with the underground water level observations as well as with seismic monitoring.
Thanks to better localization of seismic events and high sensitivity of network, the present project can
concentrate on special phenomena as very weak seismic swarms, non-volcanic tremors and migration of
hypocenters. This will help us to understand the nature of local seismicity in this region.