地形メッシュ自動分割法による重力地形補正

抄録

The effect of topographic mesh size and correction range on a terrain correction is examined by a simple stacking method of rectangles formed by mesh data of 10", 20",30", and 60" intervals, respectively. This examination shows that the mesh size affects seriously over steep gradient areas shallower than 500m depth. This fact suggests that data with finer mesh size is required for the approximation of topography near the observation point. To meet this requirement, a new method to approximate the topography near the observation point is developed: for the nearest region (within the basic mesh including the observation point), the mesh is divided into sub-meshes in accordance with depths and slopes near the observation point: for the near region surrounding the nearest region, the area is divided into 12 blocks of 1/2-size of the basic mesh. The depths at the centers of these sub-meshes are automatically interpolated from the depths at the adjacent grids and the observed point. By using the above method, the accuracy of terrain correction is improved to as much as 0.7mGal in the case of division number 8. Bouguer gravity anomalies in Suruga Bay were calculated by this method, which may reveal fine structures of Suruga Bay.