Abstract:  Gravity density inversion is to divide underground into multiple grids and calculate the density of each grid. The resolution of the current methods is low. To make an improvement，an adaptive weight function of the density inversion method was proposed. Because the upper space height anomalies highlight different buried depth of geological bodies, the corresponding space abnormal weight function iteration inversion was established to effectively improve the results of convergence and resolution. The model test shows that by using this adaptive anomaly weight density method more accurate and convergent results can be obtained compared with the conventional method, and the method has a good noise suppressing effect. Based on this inversion technique, the spatial density structure of the eastern depression was reconstructed, and the residual characteristics of Mesozoic in the eastern depression were analyzed. The results show that the distribution of Mesozoic group in the eastern depression belt is clearly different from that in the north and south. The Mesozoic group in the south (Diaobei sag) is widely distributed with large thickness(about 4 km), which overturns the previous understanding that the Mesozoic in the Xihu sag in the northern part of the basin is relatively thin, and that the Mesozoic characteristics of the two sags are the same. Diaobei sag of the Mesozoic is an epicontinental depression basin, which is limited to the central and southern part of the basin.

Key words: Diaobei sag in East China Sea, anomaly weighting function, Mesozoic, distribution characteristics, threedimensional density inversion