The oldest mine cavities of the Jeroným Mine were already mined out more than 400 years ago. That is why it is necessary to determine the stability of individual parts of underground spaces. The assessment of stability of mine cavities is based on the long-term monitoring of chosen parameters. A distributed measurement network has been operated here using several different types of sensors. A laser distance meter that is used for measuring the height of a large chamber is one of these sensors. The results obtained from this monitoring are presented. Even if no apparent correlation seems to be visible between Earth’s tides and LDM variations, some features of recorded data, like dynamical frequency crossover in the power spectrum, could be due to the tidal cycles of the Earth., Zdeněk Kaláb, Markéta Lednická, Jaromír Knejzlík and Luciano Telesca., and Obsahuje bibliografii
Thirty years long measurements of plumb line variations carried on with help of horizontal pendulums provided us information of non-tidal effects. Installation of the long water tube tiltmeter opens for us new possibility to answer the question, which part of non-tidal effects observed by means of pendulums was associated with geodynamic phenomena and which part was of instrumental or local origin. Two years long measurements of the long water-tube tiltmeter showed us some important similarities between non-tidal effects registered by both instruments: comparable amplitudes of non-tidal effects, time of durations of non-tidal effects as well as irregularity of occurring of non-tid al events. In spite of disjunction of time series of measurements obtained with help of horizontal pendulums and long water-tube tiltmeters we are able to conclude that the reasons of large non-tidal effects can not be simply explained by influence of temperature or pressure variations., Marek Kaczorowski., and Obsahuje bibliografické odkazy
We present first results of the study of possible relations between the seismic activity and crustal fluids (groundwater an d carbon dioxide) in the area of the Hronov-Poříčí Fault Zone (HPFZ), situated on the NE margin of the Bohemian Massif. Local seismic monitoring and observations of groundwater levels in deep wells and concentrations of carbon-dioxide in the mineral spring at Třtice was started in 2005. Since then, more than 30 local seismic events were observed in the area of the HPFZ. The two strongest earthquakes with macroseismic effects were recorded on August 10, 2005 (M = 2.4) and October 25, 2005 (M = 3.3). Most of the epicentres were situated along the central part of the HPFZ. Only some weak events from February and March 2006 were concentrated along the SE termination of the HPFZ. Results of the hydrological monitoring show that water level fluctuations are affected mainly by the precipitation, snow-melt, air pressure changes, and tidal deformations of the Earth’s crust. The effects of seismo-tectonic activity were detected only in one out of five water wells, where we observed several step-like water level anomalies with amplitudes of 4 to 15 cm. Two of them preceded the August 10, 2005 and October 25, 2005 earthquakes. Three other anomalies seemed to originate independently of the seismic activity. We therefore suppose that they were induced by aseismic movements along the HPFZ. Contrary to the water level fluctuations, CO2 concentrations in the mineral spring seem to be dependent on water temperature; no evident seismic-induced changes have been observed yet., Vladimír Stejskal, Lumír Skalský and Ladislav Kašpárek., and Obsahuje bibliografické odkazy
The harmonic oscillations of water level changes with several hundred nanometers amplitudes and 10-3 [Hz] frequencies are irregularly observed with the water-tube tiltmeter. The effects are observed only by one of four gauges - the one closest to the entrance to underground. The other three gauges of water-tube tiltmeters are situated at the ends of the corridors and are significantly more distant from the entrance to the underground. The atmospheric pressure signals affect level of water in the instrument by inverse barometric effect. The water-tube tiltmeters can register water level variations associated with inverse barometric effects, which were produced by air pressure signals until 10-5 [Pa] magnitude. The amplitude of harmonic oscillations of water level is significantly large and amounts to 1/10 of tidal amplitude, that is 300 to 500 nanometers, which corresponds to 5 x 10-3 [Pa] of air pressure variations. Harmonic oscillations appear irregularly and their time of duration changes from few days until several weeks. The length of atmospheric wave of 10-3 [Hz] frequencies is of 1000 [km] and cannot be explained by any phenomenon from the outside surroundings or the inside of the underground. Resonance frequencies of air column in the hundred meters long underground corridors are of the order of single Hz. Absence of similar signals in measurements from the other three gauges suggests that the harmonic signals are not propagated through the Earth’s solid body but through the atmospheric medium. The observed micro-vibrations of air pressure are very low infrasounds which can be produced in large dimension space of thousand kilometers size. The open question is what is the origin of micro-vibrations registered by the water-tube tiltmeter., Marek Kaczorowski., and Obsahuje bibliografii