南海东部海盆海山磁性对比

A study on magnetic anomalies comparisons of seamounts in the eastern Subbasin of the South China Sea

根据 1 980年～ 1 987年在南海海盆进行地球物理调查获取的海山地形和地磁异常资料 ,运用虚源法 ,对南海东部海盆区域的 9座海山作了磁性计算及对比。结果表明 :(1 )每座海山非均匀磁性反演的磁异常形态比均匀磁性反演的磁异常形态更接近观测异常 ,海山为非均匀磁化。 (2 )每座海山的非均匀磁化计算的拟合度参数值 (GFR值 )大于均匀磁化计算的拟合度参数值 (GFR0 值 ) ,平均每座海山增加 3 .7。 (3 )海山形成后均向北运移 ,位于东部海盆北侧的5座海山沿纬向位移的平均距离为 9.2 1°,南侧 4座海山沿纬向位移的平均距离为 3 .6 7°;海山均呈逆时针旋转 ,但旋转的角度存在区域性差异 ;东部海盆的运移方式与东邻的吕宋岛、西菲律宾海盆和台湾岛相一致。 (4)海山的磁化强度呈明显的分区性 ,北侧 5座海山的磁化强度大于南侧 4座海山的磁化强度 。

Based on the data analysis of the seamount topography and the magnetic anomalies obtained by the geophysical survey during 1980~1987 in the eastern basin of the South China Sea.The result,magnetic inversion and contrast to nine seamounts in the eastrn basin of the South China Sea, shows that the inversion reliability of heterogeneous magnetism is obviously better than that of homogeneous magnetism.These seamounts are heterogeneously magnetized. The goodness-of-fit ratio averagely heighten 3.7 with the method of maginary source to the inversion of heterogeneous magnetism inversion than with the routine method to homogeneous model. In comparison with the seamount magnetism parameter shows that the five seamounts in north of the subbasin moved averagely distance 9.21° along latitude toward north direction, and the four seamounts in south of the subbasin 3.67°respectively. All seamounts are anticlockwise revolution, but the size of revolution angle implies the feature of the different belt in the sea basin. The direction of motion and the modes of transformation of the eastern basin of the South China Sea are conformable to Luzon island, western of Philippine sea basin and Taiwan island. There are subregionality of seamounts magnetized intensity.The magnetized intensity of five seamounts in north of the subbasin is greater than the four seamounts in south of the subbasin. We extrapolate that the eastern basin of the South China Sea moved northward when the basin come into being.