Gyula Mentes

Influence of Temperature and Barometric Pressure Variations on Extensometric Deformation Measurements at the Sopron Station

Results of the deformation measurements obtained by a quartz tube extensometer installed at the Geodynamical Observatory of the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences in Sopron (Hungary) are described. In the same time the dependence of the deformation data on the temperature and pressure is also investigated.

Investigation of temperature and barometric pressure variation effects on radon concentration in the Sopronbánfalva Geodynamic Observatory, Hungary.

Radon concentration variation has been monitored since 2009 in the artificial gallery of the Sopronbánfalva Geodynamic Observatory, Hungary. In the observatory, the radon concentration is extremely high, 100-600 kBq m(-3) in summer and some kBq m(-3) in winter. The relationships between radon concentration, temperature and barometric pressure were separately investigated in the summer and winter months by Fast Fourier Transform, Principal Component Analysis, Multivariable Regression and Partial Least Square analyses in different frequency bands. It was revealed that the long-period radon concentration variation is mainly governed by the temperature (20 kBq m(-1) °C(-1)) both in summer and winter. The regression coefficients between long-period radon concentration and barometric pressure are -1.5 kBq m(-3) hPa(-1) in the summer and 5 kBq m(-3) hPa(-1) in the winter months. In the 0.072-0.48 cpd (cycles per day) frequency band the effect of the temperature is about -1 kBq m(-3) °C(-1) and that of the barometric pressure is -5 kBq m(-3) hPa(-1) in summer and -0.5 kBq m(-3) hPa(-1) in winter. In the high frequency range (>0.48 cpd) all regression coefficients are one order of magnitude smaller than in the range of 0.072-0.48 cpd. Fast Fourier Transform of the radon concentration, temperature and barometric pressure time series revealed S1, K1, P1, S2, K2, M2 tidal constituents in the data and weak O1 components in the radon concentration and barometric pressure series. A detailed tidal analysis, however, showed that the radon tidal components are not directly driven by the gravitational force but rather by solar radiation and barometric tide. Principal Component Analysis of the raw data was performed to investigate the yearly, summer and winter variability of the radon concentration, temperature and barometric pressure. In the summer and winter periods the variability does not change. The higher variability of the radon concentration compared to the variability of the temperature and the barometric pressure shows that besides the temperature and barometric pressure variations other agents, e.g. natural ventilation of the observatory, wind, etc. also play an important role in the radon concentration variation.

Recurring mass movements on the Danube's bank at Dunaszekcső (Hungary) observed by geodetic methods

Abstract. In September 2007 a geodetic network based on GPS measurements, precise levelling and continuous borehole tilt measurements was established for surface displacement monitoring on the high bank of the River Danube at Dunaszekcső where a serious landslide began to develop at that time. The landslide took place on February 12, 2008. After rapid, enormous movements, which resulted in significant subsidence (8–10 m) and lateral displacements (4–5 m) on the high bank at Dunaszekcső and the emergence of a peninsula consisting of clastic material in the Danubes bed, the deformation rates significantly dropped. This observation was explained by the secondary metastable equilibrium of the moving blocks at that time. However, our subsequent geodetic data clearly showed that slow post-event movements (mainly subsidence, 0.5–1.0 cm/month) on both the northern and southern sliding blocks have been occurring for the last two years, which means that the sliding blocks did not reach an equilibrium in the mentioned period. At the same time, measurements on our extended geodetic network in the second half of 2010 referred to a possible southward spread of sliding (southern part of the Vár Hill) in the near future. Later on (spring 2011), field observations were also indicative of the initiation of movements on the southern part of the Vár Hill as predicted by the geodetic measurements. The areal extent of the block becoming unstable closely corresponds with the danger zone assigned by GPS observations.

Observation of the Earth Liquid Core Resonance by Extensometers

We performed Earth tidal measurements by quartz tube extensometers of the same type at several observatories (Budapest, Pécs, Sopronbánfalva in Hungary and Vyhne in Slovakia). In this paper, the first attempts to reveal the effect of the Free Core Nutation (FCN) from strain measurements are described. The effect of the FCN on the P1, K1, Ψ1 and Φ1 tidal waves were studied on the basis of tidal results obtained in four observatories. Effectiveness of the correction of tidal data for temperature, barometric pressure and ocean load was also investigated. The obtained K1/O1 ratios are close to the theoretical values with exception of the Pécs station. We found a discrepancy between the observed and theoretical P1/O1 values for all stations with exception of the Budapest station. It was found that the difference between the measured and theoretical Ψ1/O1 and Φ1/O1 ratios was very large independently of correction of the strain data. These discrepancies need further investigations. According to our results, fluid core resonance effects can also be detected by our quartz tube extensometers but correction of strain data for local effects is necessary.

Relationships between short periodic slope tilt variations and vital processes of the vegetation

Abstract. A lot of publications deal with the effect of the root network of the vegetation on near surface slope movements but the effect of the vital processes of the vegetation on soil deformation has been less investigated till now. In this presentation relationships between vital processes of the plants and small movements of the slope are shown. For monitoring stream bank movements, two geodetic test sites were established on the high loess bank of the River Danube at Dunaföldvár and Dunaszekcső in Hungary. On the Dunaföldvár test site two and on the Dunaszekcső test site three highly sensitive borehole tiltmeters were also installed for continuous monitoring of movements. The records of the tiltmeters show a daily variation with variable magnitude in the range of some microradians. From our previous research we know that these small movements are in close connection with the ground water variations. Vegetation maps were made for both test sites. The temperature and precipitation was continuously recorded. On the basis of these data and the vegetation map the potential evapotranspiration was calculated for both sites. Values of the potential evapotranspiration and precipitation were compared to the micro-tilts of the high loess banks at Dunaföldvár and Dunaszekcső. It was pointed out that the daily tilt amplitudes are in close connection with the vital processes of the plants. Our investigation showed that the vegetation can play an important role in hindering landslides occurrence since by planting appropriate vegetation on slopes the infiltration of the precipitation into the deep layers of the slope and so the moistening of the high bank can be significantly diminished.

Extensometric observation of Earth tides and local tectonic processes at the Vyhne station, Slovakia

Abstract The Vyhne Tidal Station of the Earth Science Institute of the Slovak Academy of Sciences is located in the former mining gallery of St. Anthony of Padua in the Vyhne valley, Štiavnické vrchy Mts., Central Slovakia. It is equipped with a 20.5 metre long quartz-tube extensometer measuring Earth’s tides, and long-term tectonic deformations of the Earth’s crust. Data between 2001 and 2015 with some diverse gaps were digitally collected, processed and analysed. The effects of the local conditions, such as structure of the observatory, cavity effect, topography and geological features of the surrounding rocks, were investigated in detail and these effects were taken into consideration during the interpretation of the results of the data analysis. Tidal analysis of the extensometric data between 2005 and 2015 revealed that the measured tidal amplitudes are close to the theoretical values. The tidal transfer of the observatory was also investigated by coherence analysis between the theoretical and the measured extensometric data. The coherence is better than 0.9 both in the diurnal and semidiurnal band. The effect of the free core nutation resonance was also investigated in the case of the K1 and P1 tidal components. Since the K1/O1 ratio was about the theoretical value 0.8, than the P1/O1 was between 1.0 and 1.15 instead of the theoretical value of 0.9. The rate of the long-term strain rate was also investigated and the obtained −0.05 μstr/y shows a good agreement with the strain rate inferred from GPS measurements in the Central European GPS Reference Network.

The role of vegetation in the daily and yearly small tilt variations of the Danube’s high bank, Hungary

In this paper relationships between vital processes of plants and small movements of a river bank slope are investigated. For monitoring the movements, two geodetic test sites were established on the high loess bank of the river Danube at Dunafoldvar and Dunaszekcső in Hungary. At both sites two highly sensitive borehole tiltmeters were installed for continuous monitoring of movements. The recorded daily tilt amplitudes were compared with the precipitation and the potential evapotranspiration of the area. It was pointed out that the daily tilt amplitudes are in close connection with the vital processes of the plants. The precipitation effect on the seasonal variations of the tilt amplitudes is of minor importance which means that the vegetation has a much more important role in the water balance of the upper soil layer than the precipitation. Our investigation showed that the vegetation can be effective in hindering landslides occurrence since the infiltration of the precipitation into the deep soil layers and so the moistening of the high bank can be significantly diminished by planting appropriate vegetation on slopes.

Observing Slope Stability Changes on the Basis of Tilt and Hydrologic Measurements

Abstract In Hungary, the high loess bank of the River Danube in Dunaszekcső has been moving with varying rate since 2007. On the high bank a geodetic monitoring network was established in September 2007. At the same time two borehole tiltmeters and later two ground water level sensors were also installed. The high-sensitive tiltmeters made it possible to study the relationships between the small tilts of the high bank and the ground water levels and the water level of the River Danube. Results of the multiple regression analysis between tilt components and water levels showed that the temporal variation of the regression coefficients is in close connection with the stability of the high bank. The investigations also showed that the movements are in very strong connection with the variation of the ground water level and less depend on the variation of the water level of the River Danube. The characteristic tilt processes, 3–4 weeks before large movements, and the slope stability changes inferred from the relationships between tilts and water level variations can be useful for early warning of landslides.

Observation of Triggering Factors and Development of Landslides by Borehole Tiltmeters on the High Bank of the River Danube in Dunaszekcső, Hungary: A Case Study

In Hungary the high loess banks along the west side of the River Danube are prone to landslides that cause a lot of damage. Several landslides have occurred in Dunaszekcső. In August 2007 the commencement of a slow sliding process was visually observed here and two borehole tiltmeters were installed in the dangerous area.One instrument was placed on the stable part and the other on the unstable part of the high loess wall. A large landslide occurred here on 12 February 2008, so the whole sliding process was recorded by the tiltmeters. The instrument on the sliding part of the high bank was reinstalled one year after the slump because of the large movements. The tiltmeter on the stable part was working continuously and so the processes by which the high bank tried to keep its balance were recorded. However, the high bank did not come to an equilibrium state and in 2010 a new crack appeared about 8–10 m from the 2008 slide headwall. The recorded tilt is similar to the tilt process before the first slump. Besides tilt measurements, the water level of the River Danube, the ground water table, and the ground and air temperature were also monitored. The potential evapotranspiration of the area was also determined to study the effect of the vegetation. This paper presents the tilt processes and the relationships between tilt and hydrological and meteorological parameters.