Interferometric Water Level Tilt Meter Development in Finland and Comparison with Combined Earth Tide and Ocean Loading Models

Ruotsalainen, Hannu

doi:10.1007/s00024-017-1562-6

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…While the current configuration meets the requirements of ongoing research at CO, a two ends interferomeric level tilt meter with a base as long as 50 -100 m rises the resolution allowing for reliable detection of resonance related signals in the diurnal band and reduces unwanted drift of thermal origin considerably (Ruotsalainen, 2018).…”

Section: Observation Site and Instrumentationmentioning

confidence: 99%

“…In August 2014, the Geodetic and Geophysical Institute (GGI Sopron, Hungary) installed a 5.5 m long one end Michelson-Gale type interferometric water level tilt meter (iWT) at CO, designed by the Finnish Geodetic Institute (FGI) (Ruotsalainen et al, 2016a;2016b;Ruotsalainen, 2018). Continuous tilt measurements started at CO in order to monitor geodynamical phenomena like microseisms, free oscillations of the Earth, earth tides, mass loading effects (ocean tidal and atmospheric loading) and possible crustal deformations.…”

Section: Observation Site and Instrumentationmentioning

confidence: 99%

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Hydrological Signals in Tilt and Gravity Residuals at Conrad Observatory (Austria)

Meurers¹,

Papp²,

Ruotsalainen³

et al. 2020

Preprint

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Abstract. The Superconducting Gravimeter GWR C025 monitors the vertical component of the gravity vector at the Conrad Observatory (Austria) since autumn 2007. Two tilt meters operate continuously since spring 2016: a 5.5 m long interferometric water level tilt meter and a Lippmann-type 2D pendulum tilt sensor. The co-located and co-oriented set up enables a wide range of investigations because tilts are sensitive both to geometrical solid Earth deformations and to gravity potential changes. The tide free residuals of the SG and both tilt meters clearly reflect the gravity/deformation effects associated with short- and long-term environmental processes and reveal a complex water transport process at the observatory site. Water accumulation on the terrain surface causes short-term (a few hours) effects which are clearly imaged by the SG gravity and N-S tilt residuals. Long-term (> a few days/weeks) tilt and gravity variations occur frequently after long-lasting rain, heavy rain or rapid snowmelt. Gravity and tilt residuals are associated to the same hydrological process but have different physical causes. SG gravity residuals reveal the gravitational effect of water mass transport, while modelling results exclude a purely gravitational source of the observed tilts. Tilt residuals show the response on surface loading instead. N-S tilt signals are much stronger than those of the E-W component most probably due to the well-known cavity effect of the 150 m long tunnel oriented in E-W direction.

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Section: Observation Site and Instrumentationmentioning

confidence: 99%

Section: Observation Site and Instrumentationmentioning

confidence: 99%

Hydrological Signals in Tilt and Gravity Residuals at Conrad Observatory (Austria)

Meurers¹,

Papp²,

Ruotsalainen³

et al. 2020

Preprint

Self Cite

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show abstract

“…In August 2014, the Geodetic and Geophysical Institute (GGI, Sopron, Hungary) installed a 5.5 m long Michelson-Gale-type interferometric water level tiltmeter (iWT), recording at only one end of the tube, designed by the Finnish Geodetic Institute (FGI; Ruotsalainen et al, 2016a, b;Ruotsalainen, 2018), on a 6 m long pier in the middle of the tunnel, about 94 m away from the SG. Continuous tilt measurements started at CO in order to monitor geodynamical phe- nomena like microseisms, free oscillations of the Earth, earth tides, mass loading effects (ocean tidal and atmospheric loading) and possible crustal deformations.…”

Section: Observation Site and Instrumentationmentioning

confidence: 99%

“…The iWT scale factor is absolute and based on optical interferometry in the CO station condition. The iWT tiltmeter detects crustal tilt from water level variations at one end of the tube by interference phase values, which are converted to tilt by a conversion factor based on laser wavelength, refraction coefficient of water and tube length of the tiltmeter (Ruotsalainen, 2018).…”

Section: Observation Site and Instrumentationmentioning

confidence: 99%

Hydrological signals in tilt and gravity residuals at Conrad Observatory (Austria)

Meurers

Papp

Ruotsalainen

et al. 2021

Hydrol. Earth Syst. Sci.

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Abstract. The superconducting gravimeter (SG) GWR C025 has monitored the time variation in gravity at the Conrad Observatory (Austria) since autumn 2007. Two tiltmeters have operated continuously since spring 2016, namely a 5.5 m long interferometric water level tiltmeter and a Lippmann-type 2D pendulum tilt sensor. The co-located and co-oriented set up enables a wide range of investigations because the tilts are sensitive to both geometrical solid Earth deformations and to gravity potential changes. The tide-free residuals of the SG and both tiltmeters clearly reflect the gravity and/or deformation effects associated with short- and long-term environmental processes and reveal a complex water transport process at the observatory site. Water accumulation on the terrain surface causes short-term (a few hours) effects which are clearly imaged by the SG gravity and N–S tilt residuals. Long-term (> a few days/weeks) tilt and gravity variations occur frequently after long-lasting rain, heavy rain or rapid snowmelt. Gravity and tilt residuals are associated with the same hydrological process but have different physical causes. SG gravity residuals reveal the gravitational effect of water mass transport, while modelling results exclude a purely gravitational source of the observed tilts. Tilt residuals show the response on surface loading instead. Tilts can be strongly affected by strain–tilt coupling (cavity effect). N–S tilt signals are much stronger than those of the E–W component, which is most probably due to the cavity effect of the 144 m long tunnel being oriented in an E–W direction.

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“…However, prior to using tiltmeter corrections, the attraction part of the observed tilt should be removed as ring lasers are sensitive only to the geometrical part (Schreiber and Wells 2013). Additionally, any instrument, also a tiltmeter, has its own instrumental noises or offsets (more details on the influence of diurnal and subdiurnal signals in the normal vector about tiltmeter observations and their sensitivity to the phenomena discussed in this paper can be found in the PAGEOPH Topical volume Braitenberg et al (2018) as for instance Ruotsalainen (2018), Grillo et al (2018) and Rossi et al (2018)). Therefore, we decided to verify how the local phenomena, solid Earth tides, ocean tidal loading and non-tidal atmospheric pressure and continental water storage loading, reflect themselves in the observed Sagnac frequency and compare the modeled signal with the one observed by a tiltmeter.…”

Section: Introductionmentioning

confidence: 99%

On the Influence of Diurnal and Subdiurnal Signals in the Normal Vector on Large Ring Laser Gyroscope Observations

Tercjak

Gebauer

Rajner

et al. 2020

Pure Appl. Geophys.

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The ring laser gyroscope (RLG) technique has been investigated for over 20 years as a potential complement to space geodetic techniques in measuring Earth rotation. However, RLGs are also sensitive to changes in their terrestrial orientation. Therefore in this paper, we review how the high-frequency band (i.e. signals shorter than 0.5 cycle per day) of the known phenomena causing site deformation contribute to the RLG observable, the Sagnac frequency. We study the impact of solid Earth tides, ocean tidal loading and non-tidal loading phenomena (atmospheric pressure loading and continental hydrosphere loading). Also, we evaluate the differences between available models of the phenomena and the importance of the Love numbers used in modeling the impact of solid Earth tides. Finally, we compare modeled variations in the instrument orientation with the ones observed with a tiltmeter. Our results prove that at the present accuracy of the RLG technique, solid Earth tides and ocean tidal loading effects have significant effect on RLG measurements, and continental hydrosphere loading can be actually neglected. Regarding the atmospheric loading model, its application might introduce some undesired signals. We also show that discrepancies arising from the use of different models can be neglected, and there is almost no impact arising from the use of different Love numbers. Finally, we discuss differences between data reduced with tiltmeter observations and these reduced with modeled signal, and potential causes of this discrepancies.

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Interferometric Water Level Tilt Meter Development in Finland and Comparison with Combined Earth Tide and Ocean Loading Models

Cited by 8 publications

References 11 publications

Hydrological Signals in Tilt and Gravity Residuals at Conrad Observatory (Austria)

Hydrological Signals in Tilt and Gravity Residuals at Conrad Observatory (Austria)

Hydrological signals in tilt and gravity residuals at Conrad Observatory (Austria)

On the Influence of Diurnal and Subdiurnal Signals in the Normal Vector on Large Ring Laser Gyroscope Observations

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