Magnetic resonance sounding is a geophysical exploration method based on the difference of relaxation characteristics of hydrogen proton in geomagnetic field. It can detect the content and distribution of groundwater without damage. In recent years, with the expansion of the application of magnetic resonance sounding, this method is often faced with the detection when the surface has a large slope. When traditional inversion methods are used, inaccurate inversion results often occur. In this paper, the angle between the geomagnetic field vector and the coil is introduced, which is called the effective geomagnetic inclination, and the inversion method of the magnetic resonance sounding under surface slope is given. According to the prior information provided by geological data or other geophysical methods, the distribution of parallel or horizontal layered kernel functions of the magnetic resonance sounding is obtained, so as to carry out the inversion of the NMR signal under the condition of surface slope. In this paper, 1D and 2D aquifer models are constructed with the sloping surface, the corresponding NMR signals are obtained by forward calculation, and the kernel functions calculated by effective geomagnetic inclination and traditional method are used for inversion. The results show that, in the case of surface slope, the traditional inversion method of magnetic resonance sounding will inevitably produce errors, while the kernel function calculated by effective geomagnetic inclination can suppress the influence of surface slope. The validity and feasibility of the method were verified by the inversion of the filed NMR data in Baishuihe landslide area. Therefore, the inversion method based on the effective geomagnetic inclination proposed in this paper can greatly improve the application scope of magnetic resonance sounding.
李凡, 周明, 李开天, 鲁恺, 李振宇. 单斜地形情况下的磁共振测深方法反演研究[J]. 物探与化探, 2021, 45(3): 712-725.
LI Fan, ZHOU Ming, LI Kai-Tian, LU Kai, LI Zhen-Yu. Inversion of magnetic resonance sounding under the condition of surface slope. Geophysical and Geochemical Exploration, 2021, 45(3): 712-725.
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