海区沉积盆地的三维变密度基底反演及其应用

建立了适合海区沉积盆地基底反演的密度模式，推导了对应的重力异常精确公式（近区计算公式）和近似公式（远区计算公式），提出模拟沉积盆地复杂变化的密度差－深度曲线的分段拟合方法。建立了一种利用地震波速度谱、重力和水深资料反演沉积盆地基底的方法。利用地震波速度谱的资料对厦澎凹陷的密度－深度关系进行了统计分析，并反演了厦澎凹陷的重力基底，认为整个厦澎凹陷可能由不同构造格局的东北和西南两部分组成，并分别讨论了这两部分的基底特征。

3-D GRAVITY INVERSION WITH VARIABLE DENSITY FOR THE BASEMENT OF SEDIMENTARY BASIN IN SEA AREA AND ITS APPLICATION

The density models for calculating basement of sedimentary basin in sea area by gravity inversion were set up in this paper, and the accurate and approximate formulas for calculating gravity anomalies were derived. The fitting method by divided segments for complicated variable density contrast-depth curves in sedimentary basin was proposed. A method of gravity inversion for calculating basement of sedimentary basin using the data of seismic velocity spectrum, gravity anomalies, and water depth was built up. The relationship between density and depth derived from the seismic velocity was discussed by statistical method, and the basement of sedimentary basin was calculated from gravity data in Xia Pan Depression. Based on the calculated results, we thought that Xia Pan Depression was possibly formed by two parts in tectonic structure: trending northeastward and southwestward parts, and described their features in basement.