Abstract
An adaptive mesh form of the gravity-geologic method, known as improved Gravity-Geologic Method (iGGM), was implemented on free-air gravity anomalies and shipborne depths to obtain an improved 1′ × 1′ bathymetry model of the Gulf of Guinea (15°W–5°E, 4°S–4°N). An optimal density contrast of 8000 kg/m3 was used for the whole area. The iGGM model compared well with NGDC, ETOPO1, and SIO models; with difference standard deviations and correlation coefficients being 180.20 m, 0.9248, 184.34 m, 0.9551, and 179.84 m, 0.8886, respectively. These prove generally that iGGM is efficient for estimating bathymetry with limited shipborne depths. The influence of shipborne depths quantity and optimal density contrast on bathymetry inversion are analysed, respectively, for the whole region and three subregions (15°W–8°W, 4°S–2°N; 7°W–2°E, 2°S–2°N; and 1°E–5°E, 4°S–0°N). Results showed that, compared with the mountainous areas, higher inversion accuracy (standard deviation of test differences less than 50 m) is achievable in the low-lying region using fewer shipborne depths. With 75% of shipborne depths used for the entire model, the standard deviation of differences between iGGM and shipborne depths at test points was 184.74 m. This indicates that to further improve the region’s bathymetry, more ship sounding is required in the mountainous areas. Numerical results showed different optimal densities should be selected for different areas, especially for the mountainous areas. Using a common density contrast in the whole region may limit the accuracy of the bathymetry inversion.
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Acknowledgments
The authors are grateful to NOAA for providing the ship depth data and DTU for providing the gravity anomaly data. Again, we are thankful to SIO for their model; as well as Natural Earth for providing shapefile and raster data of the globe.
Funding
This work is funded by the National Natural Science Foundation of China (No. 41674026), the Fundamental Research Funds for the Central Universities (No. 2652018027), the Open Research Fund of Key Laboratory of Space Utilization, the Chinese Academy of Sciences(LSU-KFJJ-201902) and Qian Xuesen Lab.—DFH Sat. Co. Joint Research and Development Fund under grants(M-2017-006).
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Annan, R.F., Wan, X. Mapping seafloor topography of gulf of Guinea using an adaptive meshed gravity-geologic method. Arab J Geosci 13, 301 (2020). https://doi.org/10.1007/s12517-020-05297-8
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DOI: https://doi.org/10.1007/s12517-020-05297-8