最佳向上延拓高度的估计

提出根据两个相邻高度重力异常向上延拓值相关系数与高度的关系 ,以估计应用向上延拓分离区域及剩余重力异常的最佳向上延拓高度的方法。二维模型计算表明 ,不同高度的观测重力异常向上延拓值和观测面上区域重力异常值的互相关系数与高度的关系曲线 ,存在一个明显的极大值 ;这个极大值对应的高度 ,就是从观测异常中分离出这一区域重力异常所需要的最佳向上延拓高度。两个相邻高度重力异常向上延拓值之间的互相关系数与高度的关系曲线 ,存在一个明显的转折点 ,这个转折点对应的高度 ,就是所求的最佳向上延拓高度。应用本方法处理华南北部地区布格重力异常的结果表明 ,由于引起本区区域重力异常的地质因素 ,除了莫霍面及上地壳底面外 ,还受到本区广泛分布甚至出露的花岗岩的影响 ;所以为了从观测异常中分离这一区域异常所需要的最佳向上延拓高度为 2 0 0km ,小于莫霍面及上地壳底界面的平均深度。为了从观测异常中分离出由莫霍面引起的重力异常所需要的向上延拓高度 ,达到 15 0km。因此 ,应用本方法处理实测重力资料 ,必须首先了解引起区域重力异常的场源情况。

ESTIMATION OF OPTIMUM UPWARD CONTINUATION HEIGHT

A method for estimating an optimum upward continuation height for regional\|residual gravity separation is presented. The method is based on cross\|correlation between upward continuations of gravity anomalies to two successive heights. Two\|dimensional model study shows that a distinct maximum exists at the optimum height on a graph of cross\|correlation between the upward continuation of gravity anomalies to different heights and real regional anomaly at observation level against the heights. The optimum height can be estimated from the point of discontinuity of the gradient on a graph of cross\|correlation between the continuations of gravity anomalies to two successive heights versus the heights. Application of the method to the Bouguer anomaly in South China shows the effectiveness of the method. However, because the regional anomaly is caused by the Moho and the upper crustal thickness variations, and is interfered by the extensive shallow granites in this area, the estimated optimum height from the cross\|correlation between the continuations of gravity anomalies to two successive heights is 20 km, which is smaller as compared with the average depth of 33 km to the Moho and the average depth of 22 km to the upper crust. Therefore, the deep sources producing the regional anomalies should be understood during using the method to process observed gravity anomaly.