Abstract:

The calculation of gravity terrain correction is a very difficult task but very an important in complete Bouguer gravity anomaly maps. To save computing time, it is necessary to find the smallest radius of the inner and outer zones that will still meet the accuracy requirement of terrain correction. (Note that the choice of radius will also depend on the roughness of the terrain under study). To see how the inner radius affects the terrain correction, we must be taken into account if the required accuracy of terrain correction is with high reliability. It is also important to determine the smallest outer radius beyond which the terrain effect can be neglected. In this study, gravity terrain corrections for mainland territory of Vietnam are calculated using a method devised from Nagy (1966) and Kane (1962). The computation was done for an inner distance of 2 km, an outer distance of 70 km with an average rock density of 2.67 g/cm3. Our results show that corrections are lower than 10 mGal for over half of the studied area, the corrections are smallest (less than 2mGal) in the plain areas and highest (approximately 21 mGal) in the northern mountainous areas. When connected for terrain, we completed Bouguer gravity anomaly by International formula 1980 for the whole territory of Vietnam, with map at 1/500.000 scale.