重力密度反演的自适应异常权函数法及其对东海钓北凹陷地层结构划分

Adaptive Weight Density Inversion Method for Gravity Anomaly and Mesozoic Division of Diaobei Sag in East China Sea

重力密度反演通过将地下剖分为多个网格,计算每个网格密度的方式来实现,现今方法计算结果分辨率较低。本文提出自适应权函数三维密度反演方法,通过上半空间不同高度异常凸显不同埋深地质体的特征,建立相应的空间异常权函数进行迭代反演,从而提升结果的收敛性和分辨率。模型试验表明,自适应异常权函数密度反演方法相对已有方法能有效提升分辨率和精度,且具有良好的抗噪声干扰能力。利用所提出的反演方法重建东海陆架盆地东部坳陷带空间密度结构,分析东部坳陷带中生界残留分布特征。结果表明,东部坳陷带内中生界分布南北差异明显,南部钓北凹陷中生界广泛分布,厚度较大,约4 km,颠覆了以往盆地北部西湖凹陷中生界较薄、两个凹陷中生界特征一致的认识。因此钓北凹陷中生界为陆缘坳陷型盆地,盆地范围局限于现今盆地中南部。

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.