关键词: 激发极化法, 起伏地形, 等效电阻率, 有限元, 非结构, 三维正演

Abstract: It is generally believed that the undulating terrain has little influence on the induced polarization (IP) exploration, because it has no influence under the relatively ideal condition of uniform polarization of the underground medium. However, for the complex medium model with ore body under the condition of undulating terrain, the terrain will certainly have an impact on the induced polarization method. Three have been very few studies on the quantitative characterization of terrain effect on the induced polarization method,mainly because the undulating terrain is not easy to simulate, especially for the three-dimensional model. In this paper, the three-dimensional unstructured finite element numerical simulation of induced polarization is developed. The unstructured mesh is particularly suitable for the numerical simulation of three-dimensional geoelectric model under arbitrary undulating terrain and the study of its influence on induced polarization. With the newly developed method, the three-dimensional induced polarization numerical simulation for plate-shaped and spherical anomaly bodies in rolling terrain is carried out, and the influence of rolling terrain on induced polarization response is discussed. The results show that the asymmetric topography will make the center position of IP anomaly deviate. The larger the slope gradient is, the larger the deviation will be, and the IP amplitude becomes smaller with increasing slope gradient. The asymmetry of polarization anomaly also plays an important role in the topography impact for its IP response.

Key words: induced polarization method, uneven terrain, equivalent resistivity, finite element method, unstructured, 3D forward modeling