磁总场异常垂直梯度三维相关成像

3D correlation imaging of the vertical gradient of magnetic total field anomaly

本文提出了磁总场异常垂直梯度三维相关成像方法,用于成像地下等效磁源分布.它首先将地下待成像空间划分为三维规则网格,然后直接计算每个网格节点磁偶极子在观测面理论磁总场异常垂直梯度与实测磁总场异常垂直梯度的互相关,其相关系数值表征等效磁偶极子分布(即磁偶极子发生的概率).理论长方体组合模型数据和实际某矿区磁测资料试验结果表明本文方法计算得到的相关系数值能基本反映地下的磁源分布,且分辨率明显高于磁总场异常三维相关成像的分辨率,也高于基于熵滤波分离异常的磁总场异常三维相关成像的分辨率.

We present a new correlation imaging approach for the vertical gradient of magnetic total field anomaly for deriving an equivalent magnetic sources distribution of the subsurface. In this approach, we divide the subsurface space into a 3D regular grid, and then at each grid node calculate cross correlation between the vertical gradient of observed magnetic total field anomaly and the vertical gradient of theoretical magnetic total field anomaly due to a magnetic dipole source. The resultant correlation coefficients are used to describe equivalent magnetic dipole distribution in a probability sense. The tests on the synthetic data and the real data show that the equivalent magnetic dipoles distribution derived by the approach basically reflects the causative sources of the subsurface, and also illustrate that its resolution is higher than both that from 3D correlation imaging for magnetic total field anomaly and from 3D correlation imaging based on entropy filter for magnetic total field anomaly.