Tuesday 23 August 2005

G3
1330-1530 hours

177
First results of a multitechnique campaign for studying ocean loading effects in
Brittany, France
Bouin, Marie-Noelle¹, Llubes, Muriel², Florsch, Nicolas³, Amalvict, Martine⁴, Boy, Jean-Paul⁴, Durand, Stéphane⁵, Esnoult, Marie-France⁶, Masson, Frederic⁷, Morel, Laurent⁵, Nicolas, Joelle⁵
1 Institut Geographique National, Marne La Vallee, France
2 Observatoire Midi Pyrenees, France
3 Universite Paris 6, France
4 EOST, France
5 Ecole Superieure des Geometres Topographes, France
6 Institut de Physique du Globe de Paris, France
7 ISTEEM, France
Author email: bouin@ensg.ign.fr
A field experiment has been conducted in 2004 in West Brittany and Cotentin (France) in order to accurately measure the 3D deformations and gravity changes due to ocean loading. Ocean loading effects are huge in West Brittany and induce deformations up to 8cm on the vertical component, with semi diurnal main period and some non linear terms. This campaign included absolute and relative gravity measurements, tiltmeters, 12 temporary GPS stations and 5 permanent stations. A Satellite Laser Ranging station was operated during one month. Most instruments were running continuously during 6 months (March to June, September to October) with two main collocated sites (Brest and Cherbourg). These data sets have been carefully analyzed (especially GPS, in order to deal with short period signals, ambiguity resolution, reference frame effects and properly separate Tropospheric perturbations). Collocated techniques analysis results have been compared to retrieve a complete information on a given site effects. We present here results of our long term series analysis of GPS, gravimetry and tiltmeters in comparison with up to date ocean tide model predictions (FES2005).

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