Gravity Terrain Corrections of Taiwan

An island-wide gravity survey was conducted from 1980 to 1987 in Ta i wan. In total, 603 gravity stations had been surveyed. Among them, 308 stations were located at elevations of 500 m or greater. Since a significant portion of our gravity stations were in mountainous areas, the terrain cor rection must be carefully estimated in the processing of gravity data. In this study, two methods, the Hammer method and the line mass integral method, are jointly used to compute the terrain corrections. The corrections are made to a distance of 100 km with an average density of 2.57 g/cm 3 The results show that the corrections of more than half of the areas in Taiwan are larger than 10 mgal. The corrections in the western coastal plain are less than 2 mgal. Higher corrections are in mountainous areas, mostly over 20 mgal. The maximum correction reaches 93 mgal on Yushan. We also find that to pographic relief in the vicinity of the station plays an important role in the correction, and the topographic effect can be ignored in marine gravity survey around Ta iwan, except off the coast along the Su-hua highway.