应用重力地质法反演马里亚纳海沟地形

Predicting Bathymetry in Mariana Trench Using Gravity-geologic Method

根据重力地质法(Gravity Geological Method,GGM),利用6736个已知水深点数据和卫星测高重力异常反演了马里亚纳海沟(142°36′~147°18′E,23°~27°N)1′×1′分辨率的海底地形,该计算中的密度差常数为1.20 g/cm^3。将反演的地形与实测检核水深数据相比,两者较差标准差为152.9 m,平均误差为(±3.0)m,均方差为153.0 m,优于ETOPO1模型和直接把船测水深控制点格网化后的模型。将重力地质法反演的模型、ETOPO1模型、直接格网模型进行功率谱密度分析,结果显示3种模型在中长波地形能量一致,但对于短波地形,重力地质法模型能量高于其他2个模型,说明重力地质法更能描绘细致的海底地形地貌。选取2条测线与重力地质法模型进行对比研究,结果表明重力地质法在海底地形起伏小的区域优于在海底地形起伏较大区域的反演效果。

Based on the gravity geology method(GGM),this study inverted the submarine topography of the Mariana Trench(in the range of 142°36′-147°18′E,23°-27°N)by using 6736 known-depth points(controlling points)and satellite altimetry gravity anomalies and density contrast of 1.2 g/cm.The standard deviation between the inverted topography and known-depth points(checking points)is 152.9 m,with an average error of(±3.0)m,mean square deviation of 153.0 m,which are better than ETOPO1 model and the gridded model which was directly interpolated from controlling points.This study then analyzed the power spectral densities of GGM model,ETOPO1 model and gridded model,and the results showed that these three models have the same energy in long and middle wave topography,but in short wave topography,the energy of GGM model was higher than the other two models,indicating that GGM method could better describe the detailed seabed topography and landform.Finally,two checking lines were selected to compare with the GGM model,and the results showed that the GGM method had a better inversion effect in the area with small topography relief than in those with large topography relief.