The long water-tube tiltmeter observations of the plumb line variations were begun about four years ago. Since 2001, twice, the instrument registered strong plumb line variations associated with earthquake. Earthquake in September 2003 made opportunity for verification of hydrodynamic system of tiltmeter. We obtained in observations large number of cycle-slip effects, which made impossible correct interpretation of data during main phase of phenomenon. Results of tests of dumping system of water waving helped us to introduce some improvements in hydrodynamic system of instrument. Catastrophic earthquake with magnitude 9.1 which took place in the area of Indian Ocean on 26th December 2004 generated phenomenon of the Earth free oscillations associated with anomalous plumb line variations of the order of single milliseconds of arc (mas). The effects of surface waves passing associated with Earth free oscillations were registered by the tiltmeter as series of anomalous plumb line variations. Surface waves produced several milliseconds of arc amplitude of plumb line variations. Results of observations showed that low-pass filters considerably reduce contribution of short-period effects and effectively protect hydrodynamic system of instrument against resonance. Nevertheless during first two hours of phenomenon cycle-slip effects occurred several times. Plot of plumb line variations in space from 26th December 2004 showed us large complication of tilt signals as well as dominated role of tidal signal. Spectral analysis of the time series of the plumb line variations obtained with help of the long water-tube tiltmeter on 26 December 2004 appeared existing fundamental modes (n = 0) in the Earth free oscillations didn’t exceed 0.2 mas., Marek Kaczorowski., and Obsahuje bibliografii
a1_A water-tube tiltmeter system composed of two perpendicular tubes was installed in the underground galleries of the Geodynamic Laboratory in the Książ Castle, Central Sudetes, in 2003. The partially filled water tubes are several tens of metres in length and have high-precision interferometric recording gauges at their ends. The recording gauges continuously measure water level changes in the tubes with single-nanometer accuracy which corresponds to 0.005 milliseconds of arc of plumb line variations. The tiltmeter has recorded several events of water level variations, with a magnitude of a few hundred micrometers and a duration of tens of days. The strongest water level variations were one order greater than variations caused by tidal phenomena and occurred in different months of a year, and hence are expected to have no seasonal origin. Because of the extremely large magnitude of the phenomenon and because time of duration of signals showed no seasonal characteristics, all external sources outside the bedrock space occupied by the instrument can also readily be precluded. Each of the recorded strong signals of water level variations consists of a symmetrical and an asymmetrical component. Because of the proportion of the water system to the large-scale geodynamic sources producing water level changes, all the external geodynamic reasons can generate only symmetrical signals in the tubes. The evidence indicates episodic tilting of the instrument itself or vertical displacements of any part of the tubes, which supports the notion of active bedrock deformation. The combination of symmetrical and asymmetrical signals implies that their source is within the bedrock space in which the instrument is embedded. The events of large water level variations can be explained by non-flat relative vertical displacement of the opposite ends of the tiltmeter tubes., a2_Asymmetrical signals are particularly pronounced in the tube named 03-04, and their magnitude suggests vertical displacement of part of the tube of the order of hundreds of micrometres. The repeatability, temporal irregularity, considerable duration time and high magnitude of the strong signals lead us to attribute them to the tilting of tiltmeter bedrock due to contemporary tectonic movements of the Książ Massif. The Książ Massif consists of a rigid rock mass of Famennian−Tournaisian conglomerates cut by several large and small faults. Rock compaction can be precluded. The massif is a prominent bedrock spur carved by a deeply incised river, and its geomorphic development seems to be related to major faults. Preliminary geological study has recognized strike-slip faults, thrusts and extensional fracture zones, some with an indication of recent activity. A few minor faults cross the bedrock under the tiltmeter geodynamic system. The tiltmeter is thus likely to be recording local signals of neotectonic activity., Marek Kaczorowski and Jurand Wojewoda., 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
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