日本列島周辺の海陸統合50Mメッシュ地形データの作成とそれを用いた海陸重力地形補正

抄録

Accuracy of terrain correction strongly depends on the grid spacing of digital elevation dataset used for calculation. In and around the Japanese Islands, both 50 m mesh elevation on land area and 500 m mean bathymetric data on sea area are available. In order to simplify calculation algorithm, we firstly generated a synthesized digital elevation and bathymetry dataset whose grid spacing is approximately 50 meters by combining several available digital topographic data. We named this dataset the "Synthesized Land and Sea 50 M Mesh Topographic Data in and around the Japanese Islands-Version 2004; LS50MJ04", which has a size of about 14 GB for 2-dimensional array with 7 byte/grid. We coded a terrain correction programsimulating topography as an assembly of a rectangular parallelepiped prism and neglecting the curvature of the earth's surface. Integration of gravitational effects due to each prism on a station is truncated at 50 km. The accuracy of calculation is evaluated to be of the order of 1 mGal or less. We can calculate terrain corrections due to both land and seafloor topogra phies within one procedure. The calculated terrain correction values are more sensitive to short wavelength topographic undulations compared with our former ones, and are consistent with other works. We applied this program for nearly 600 thousands gravity measurements in and around the Japanese Islands.