磁异常模量垂向一阶导数的特征及应用

The application and characteristic of vertical first-order derivative of the total magnitude magnetic anomaly

磁异常转换模量(magnitude magnetic transforms,简称MMTs)相比传统的数据处理方法如化极、总梯度模等,其产生的异常更接近实际磁性异常体的水平位置,以便进行磁法解释.本文基于转换模量,提出了磁异常模量的垂向一阶导数的处理方法.进一步分析模量垂向一阶导数的特征可知,对于2D异常体其完全不依赖于异常体的磁化方向;对于3D异常体其弱依赖于异常体的磁化方向.模量垂向一阶导数相比磁异常模量具有更小的中心偏移量和相对峰值;相比其他磁异常转换模量而言,具有计算量小、计算方便等优点.因此,在磁法解释中,磁异常模量垂向一阶导数能更好地确定异常体的水平投影位置以及分布规模.

Comparing with the conventional magnetic transforms of reduction to the pole（RTP）, the pseudogravity field, and the analytic signal（AS） also have these properties, magnitude magnetic transforms （MMTs） produce anomalies that are closer to the magnetic sourcets true horizontal position and are simpler to interpret than traditional method of data procession. Based on MMTs, magnetic transform of vertical first-order derivative of the total magnitude magnetic anomaly（VFDMA）is introduced in this paper. For a 2D anomaly of a homogeneous causative body, the proposed VFDMA does not depend on the Magnetization orientation. So, the proposed VFDMA can completely avoid influence of strong remanent Magnetization, and it can use to at low magnetic latitude. Nevertheless, in the 3D case, such independence does not exist but slightly sensitive to the magnetization orientation and the principal extremum occur above the sources. But comparing to the total magnitude anomaly, with smaller epicenter deviation and relative peak error when utilizing the proposed VFDMA. And also, VFDMA has smaller amount of calculation and more facilitating than other MMTs. Therefore, in the magnetic interpretation, the proposed VFDMA can better determine the level of anomaly body position and size distribution. In this paper, a calculation of the VFDMA and the total magnitude magnetic anomaly of a field example from a area, southern China demonstrate the effectiveness of the program.