HR: 1330h
AN: OS42A-0832    [PDF]
TI: Absolute Height of Sea Surface by Trajectory of GPS Antennae Over Submerged Pressure Gauges
AU: Bouin, M
EM: bouin@ensg.ign.fr
AF: LAREG/ENSG, Cite Descartes 6-8 av Blaise Pascal, Marne la Vallee, 77455 France
AU: Calmant, S
EM: stephane.calmant@cnes.fr
AF: LEGOS-UMR5566 - Observatoire Midi-Pyrenees, 18 av Edouard Belin, Toulouse, 31401 France
AU: Cheng, K
EM: cheng.168@osu.edu
AF: Departement of Civil and Environmental Engineering and Geodetic Science, Ohio State University, 222A Bolz Hall 2070 Neil Avenue, Columbus, 0H 43210 United States
AU: * Ballu, V
EM: ballu@ipgp.jussieu.fr
AF: Laboratoire de Gravimetrie et Geodynamique - IPGP, 4 place Jussieu, Paris, 75252 France
AU: Shum, C K
EM: ckshum@osu.edu
AF: Departement of Civil and Environmental Engineering and Geodetic Science, Ohio State University, 222A Bolz Hall 2070 Neil Avenue, Columbus, 0H 43210 United States
AU: Testut, L
EM: Laurent.Testut@cnes.fr
AF: LEGOS-UMR5566 - Observatoire Midi-Pyrenees, 18 av Edouard Belin, Toulouse, 31401 France
AB: Water height data provided by seafloor tide gauges is a combination of sea-level variations and ground motion. Both of these signals are of scientific interest, but they must be separated in order to be useful. Estimating ground motion is specially important in very tectonically active areas such as the Pacific Ocean rim. One promising method to separate the two contributions is to use satellite altimetry data which gives absolute water height, but these data must be calibrated using ground truth measurements. Once different components of the signal are separated, bottom pressure gauges can be used to detect vertical movements of the seafloor such as co-seismic or slow inter-seismic motions.\\ The Vanuatu archipelago is part of the Pacific ring of fire, where plates are rapidly converging. In the area, movements are very rapid and the seismic activity is intense, which gives a good opportunity to study deformation and seismic cycle. To get an integrate picture of vertical deformation over one plate and between the two plates, one needs to be able to monitor vertical movements on both underwater and emerged areas. We conducted an experiment in the Vanuatu archipelago, South-West Pacific, to compare measurements from bottom pressure gauges located beneath altimetry satellite tracks with sea surface altitude measurements from GPS. Two bottom pressure gauges are immerged since Nov. 1999 on Sabine bank (15.90$\deg$S, 166.14$\deg$E) and Wusi Bank (15.34$\deg$S, 166.55$\deg$E), West of Santo island, Vanuatu. In order to perform absolute calibrations of JASON and ENVISAT altimeters that overfly the Wusi and Sabine banks, respectively, we performed GPS measurements of instantaneous sea surface altitude. The GPS antennae were fixed on top of the 30m long R/V Alis. An inertial unit also recorded the high frequency vessel motions. The height of the antennae over the sea surface was measured using a laser distancemeter in calibration sessions during particularly calm sea states. We present results of GPS computations in kinematic mode, together with the corrections for pitch and roll from the inertial unit. We compare the results with the sea level variations recorded by the tide gauges.
DE: 1294 Instruments and techniques
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 4294 Instruments and techniques
DE: 4556 Sea level variations
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting