Time Dependencies Between Tectonic Activity of Świebodzice Depression (SW Poland) and Seismic Activity in Poland and Czech Mining Regions

Abstract

Since the 1970-ties, large azimuth changes in the equilibrium of quartz horizontal pendulums have been irregularly registered in the Geodynamic Laboratory in Książ. However, azimuth changes of the pendulums did not correlate with meteorological phenomena and the compensation phases of these changes excluded processes of gravitational creep of the rock massif. It was assumed that changes of these azimuths result from tectonic tilt of the rock massif. These were the first observations of contemporary tectonic activity in the Świebodzice Depression (SW Poland). Multiannual observations have allowed for determining temporal and amplitude characteristics of such tectonic activity. Intervals of tectonic activity last from several days to two weeks and are separated by periods of low activity or even no activity. During tectonic events, amplitudes of rock massif deformation reach values of several tens of tidal amplitudes. The distinguished characteristics of tectonic effects and their incidental character have been confirmed by water-tube tiltmeters (WT) activated in the Geodynamic Laboratory in the early 2000s. Unique conditions of the rock massif cause that the WTs, in connection with blocks of the rock massif separated by faults, are natural detectors of tectonic activity, allowing to determine the function of tectonic activity and its derivatives in the surrounding areas.