HR: 0800h
AN: G41A-0352    [Abstracts]
TI: Study of Ocean Loading Effects in Brittany, France, From a Multi-Software Analysis of 6-Months GPS Data.
AU: * Vergnolle, M
EM: mathilde.vergnolle@esgt.cnam.fr
AF: ESGT/CNAM, 1 Boulevard Pythagore, Le Mans, 72000 France
AU: Durand, S
EM: stephane.durand@esgt.cnam.fr
AF: ESGT/CNAM, 1 Boulevard Pythagore, Le Mans, 72000 France
AU: Morel, L
EM: laurent.morel@esgt.cnam.fr
AF: ESGT/CNAM, 1 Boulevard Pythagore, Le Mans, 72000 France
AU: Nicolas, J
EM: joelle.nicolas@esgt.cnam.fr
AF: ESGT/CNAM, 1 Boulevard Pythagore, Le Mans, 72000 France
AU: Bouin, M
EM: bouin@ensg.ign.fr
AF: ENSG/LAREG, 6 et 8 avenue Blaise Pascal, Marne la Vallée, 77455 France
AU: Masson, F
EM: Frederic.Masson@dstu.univ-montp2.fr
AF: UMR5573 ISTEEM, Université Montpellier 2,4 place Emile Bataillon, Montpellier cedex 05, 34095 France
AB: In northwestern France, ocean tides can reach up to 10 m and induce crustal displacements up to 12 cm peak-to-peak on the vertical component and cm-level displacements on the horizontal components. Hence, this region is particulary suited for studying ocean loading effects. Former geodetic experiments, which showed 3D crustal displacements with semi-diurnal main period and some non linear terms, were carried out in Brittany in 1998 and 1999 but lasted only 3 days. In order to confirm these former results and to go further in the study of the ocean loading effects in Brittany, a new national multi-techniques campaign (GPS, gravimetry, inclinometry, tide gauges, laser ranging, barometry) was realized in 2004. In particular, the GPS experiment was conducted on 12 and 6 local stations from March to June and September to October 2004 respectively. First, we present the GPS time series obtained from a global analysis with the GAMIT 10.2 GPS software. We show a good first order agreement between these times series and up to date ocean tide model predictions (FES2004) in terms of amplitude and main period. Then, in order to understand the discrepancies and refine our results, we test two other GPS softwares (Gipsy Oasis II (Precise Point Positioning strategy) and Bernese 5.0), and various processing strategies for the positioning and the reference frame definition. The joint analysis of the resulting time series allow us (1) to better determine the GPS resolution we can expect in ocean tide loading studies, (2) to better attribute the discrepancies between GPS time series and model to GPS accuracy, software or strategy limitations and/or to effect not taken into account in the model, and (3) to better understand the geophysical processes that govern the Earth response to ocean tide loading.
DE: 1211 Non-tectonic deformation
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: Fall Meeting 2005