Satellite Altimetry and Gravimetry Data for Mapping Marine Geodetic and Geophysical Setting of the Seychelles and the Somali Sea, Indian Ocean

Evaluation of the representative cartographic techniques demonstrated that there are still considerable challenges facing the methods of marine geodetic, geophysical and bathymetric data visualisation. In an oceanic seafloor formation, the interaction between the geological structural elements and topographical relief can be analysed by advanced mapping. In present study, a correlation between geodesy, geophysics and topography has been examined including the following variables: geological structure, coastal topography and bathymetry, geophysical fields, free-air gravity anomalies and geoid undulation, sediment thickness, bathymetric patterns, and extension of the transform faults. The variables were visualised on the high-resolution raster grids using Generic Mapping Tools (GMT) scripting toolset. The study area is located in the Seychelles and the Somali Sea segment of the Indian Ocean. The data incorporates satellite-derived gravity grid, EGM-2008, geological structures, topography from GEBCO grid and GlobSed sediment thickness, processed by GMT scripts. The results demonstrated that western continental slope of Somalia is wide, gently declining to the seafloor at depths exceeding-5000 m. Kenya and Tanzania present a wide continental foot with depths ranging from-3500 to-5000 m. The Somali Sea basin shows low sedimentation lower than 500 m, while ridges and island chains have higher sediment influx (1,000-2,000 m). The Mozambique Channel has dominating values at 2,500-3,500 m. Higher values are noted near the Reunion and Mauritius islands until the Seychelles via the Mascarene Plateau (500-1,000 m) against the <500 m in the areas of the Mid-Indian Ridge, Carlsberg Ridge and open water.