Asymmetry of the Earth and Its Shape by Gravity Method

Based on satellite gravity and geoid observation results, we calculated and analyzed different order and degree of harmonic function of geoid, which can express earth shape. It is found that 26 degree geoid anomaly shows the fundamental shape of earth shape asymmetry, and geoid anomaly of more than 6 degree only shows the local undulation character of the earth shape. Moreover, The authors inverted three dimensional global mantle density (anomaly) combining geoid data and seismic tomography data by means of damping least square method. The density anomaly result shows that mantle density is obviously inhomogeneity not only in horizontal direction, but also in radial direction. Comparing low degree geoid anomaly with mantle density anomaly, The authors think the earth shape asymmetry is mainly caused by lower mantle density inhomogeneity.