The Gravimetric Observatory J9, located near Strasbourg, France has a long history of recording solid Earth tides. We present here one of the longest gravity record (1973-2011) from three different instruments operating at the J9 station: a LaCoste-Romberg spring gravimeter (ET005) from 1973 to 1985, a GWR tidal (TT70-T005) superconducting gravimeter from 1987 to 1996 and a GWR compact superconducting gravimeter (C-026) since 1996. We give the results of a tidal analysis performed with ETERNA on these data sets. We compare the amplitudes and phases of the tidal constituents according to the instrument type. We show the improvement in noise level from the oldest type to the newest one. We also check the time stability of the observed tides for every instrument using theoretically predicted solid and ocean loading tides. This stability is also dependent on the stability of the scale factor of the cryogenic gravimeter which is derived from a direct comparison with repeated absolute gravity measurements. Finally we attempt to perform a unique tidal analysis on the entire time period (more than 37 years) in order to achieve the most precise determination of the tides in terms of signal to noise ratio and spectral resolution. From these analyses we also investigate the time stability of the diurnal waves around the liquid core resonance (K1,ψ1 and O1), in order to improve the assessment of the free core nutation (FCN) eigenperiod..
Study of the time stability of tides using a long term (1973-2011) gravity record at Strasbourg, France / M., Calvo; S., Rosat; J., Hinderer; H., Legros; Riccardi, Umberto; J. P., Boy. - (2011). (Intervento presentato al convegno IUGG2011 General Assembly tenutosi a Melbourne (Australia) nel 28 Giugno - 7 Luglio 2011).
Study of the time stability of tides using a long term (1973-2011) gravity record at Strasbourg, France
RICCARDI, UMBERTO;
2011
Abstract
The Gravimetric Observatory J9, located near Strasbourg, France has a long history of recording solid Earth tides. We present here one of the longest gravity record (1973-2011) from three different instruments operating at the J9 station: a LaCoste-Romberg spring gravimeter (ET005) from 1973 to 1985, a GWR tidal (TT70-T005) superconducting gravimeter from 1987 to 1996 and a GWR compact superconducting gravimeter (C-026) since 1996. We give the results of a tidal analysis performed with ETERNA on these data sets. We compare the amplitudes and phases of the tidal constituents according to the instrument type. We show the improvement in noise level from the oldest type to the newest one. We also check the time stability of the observed tides for every instrument using theoretically predicted solid and ocean loading tides. This stability is also dependent on the stability of the scale factor of the cryogenic gravimeter which is derived from a direct comparison with repeated absolute gravity measurements. Finally we attempt to perform a unique tidal analysis on the entire time period (more than 37 years) in order to achieve the most precise determination of the tides in terms of signal to noise ratio and spectral resolution. From these analyses we also investigate the time stability of the diurnal waves around the liquid core resonance (K1,ψ1 and O1), in order to improve the assessment of the free core nutation (FCN) eigenperiod..I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
