利用重力和地形观测反演中国及邻区地壳厚度

INVERSION OF GRAVITY AND TOPOGRAPHY DATA FOR THE CRUST THICKNESS OF CHINA AND ITS ADJACENCY

尝试了直接利用布格重力数据和地形数据反演计算中国及邻区的地壳厚度的方法.为减小区域不均衡性和重力反演中的不唯一性的影响,本方法利用地表地形起伏修正传统反演方法中的参考深度,并经过多次的迭代使得反演结果逼近真实值.在此基础上,绘制了中国及邻区1°×1°网格的地壳厚度图,对中国及邻区的布格重力异常和莫霍界面的起伏数据进行了相关性分析,其相关性系数为-0.993.其地形起伏与莫霍界面的起伏之间也呈现出了海、陆不同的线性相关,其相关系数分别为0.96和0.91.相关性计算结果显示,重力数据揭示的大陆和海洋的交界大致为水下800m.为了探讨地球曲率对该算法可能的影响,还分别计算了分区反演以及整体区域反演两种模式,研究发现两者得到的地壳厚度偏差在5km以内,并分析了可能产生偏差的原因.比较本文结果与地震测深及其它研究结果表明,独立使用布格重力异常和地形数据,能较为可靠地反演出中国及邻区地壳厚度.

The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with regional topography relief, and performed multiple iterations to make the result more reliable. The obtained crust thickness of China and its adjacenty is plotted on a map in cells of 1°× 1°. Then we analyzed the correlation between the Bouguer gravity anomaly and fluctuation of the Moho depth. A good linear correlation is found, with a correlation coefficient of -0. 993. Different correlation coefficients, 0.96 and 0.91, are found for the data in land and ocean region, respectively. The correlation result also shows that the boundary between land and ocean is generally along the bathymetric line of -800 m. In order to examine the influence of the Earth＇s curvature on the calculated result, we tried two inversion models： the inversion for the whole region and the inversion for 4 sub-regions. The difference in the crust thickness deduced from the two models is less than 5 km. Possible explanation for the difference is discussed. After comparing our result with that of other studies, we suggest that with our method the Bouguer gravity and the topography data can be independently inverted to obtain the crust thickness of China and its adjacency.