基于改进tilt梯度的三维磁异常解释技术

3D magnetic data interpretation based on improved tilt angle

当工区存在强剩磁或范围较大时,化极处理很难获得满意结果。为此,本文基于tilt梯度,推广得到可以突出x、y方向信息的tilt梯度分量,并根据这两个分量的水平导数,提出了改进tilt梯度水平总梯度的三维磁异常解释技术。该方法可以直接计算三维磁异常,无需化极。理论模型实验表明,相对于其他常用的磁数据处理方法,本文方法可以有效识别不同磁化方向下的长方体边界及球体质心的水平位置,具有更高的分辨率和精度。将该方法应用于中国内蒙塔木素地区航磁数据,解释结果与地质资料及地震推断结果对应较好,为研究区圈定隐伏磁性体提供了依据。

The delineation of magnetic anomaly and the division of structure are the important contents of the magnetic exploration.There is often no correspondence between the magnetic anomaly and the geologic body because of the influence of magnetization direction.At present,most methods for 3 D magnetic interpretation require the magnetic anomaly reduced to the pole beforehand.However,it is difficult to achieve satisfactory results by reduction to the pole when a study area is relatively large or magnetic anomaly contains remanence.In addition,magnetic reduction to the pole may bring errors,which results in the failure of exploration.This paper proposes a 3 D magnetic interpretation technique that can be directly used without reduced to the pole of magnetic anomaly.The proposed method is based on improved tilt angle,which can highlight the information of magnetic sources in the x and y directions.Model tests show that the proposed method can effectively identify the horizontal positions of the boundaries of prisms and sphere’s centroid.Furthermore,the proposed method achieves better resolution and better identification of magnetic anomaly compared to other methods.The proposed method is applied to aeromagnetic data from Tamusu of Inner Mongolia,North China,and obtains detailed information of magnetic sources.The results have good correspondence with the geological data and seismic interpretation.In addition,the calculation results of the proposed method provide guides for delineation of hidden magnetic sources in the study area.