COMPARISON AND ANALYSIS OF THE EFFECTIVE OBSERVATION AREA OF THE TENSOR CSAMT BY NUMERICAL MODELING

According to the response formulas of the scalar CSAMT (controlled source audio-frequency magnetotelluric) method, its programs can be designed in several manners with different sources such as a vertical double dipole source and a three-dipole source of varied geometries. Through numerical simulation, this study obtains the value distributions of X- and Y-direction components of the resultant electromagnetic (EM) field, which permit to further analyze the effective observational area. The results show that the distribution of crosslike source exhibits scattered weak responses, representing a smaller effective observational zone. Meanwhile, its requirement to the terrain condition of the working site is very harsh, thus cannot work well in mountainous areas with high topographic relief. Based on the principle of the rotating three-dipole device, we propose a new device composed of multiple dipole sources for the CSAMT which can facilitate integrated measurement of tensors of the EM field. Compared with the cross-like source, this approach can realize measurement throughout the whole area without weak-value zones. Moreover, this new device is easy to deploy in various terrains. The results of this study provide a technical basis for further engineering production of tensor measurement.