可控源电磁法倾子响应的三维正演

为克服天然场源的大地电磁磁场信号弱、易受电磁干扰、倾子资料计算难度大等不足,提出了可控源电磁倾子资料观测、处理与解释方法。通过可控源频域电磁法三维正演的磁场三分量,依据倾子定义计算了三维异常体在地面的倾子参数,绘制了异常体上方不同测点的倾子振幅、相位、实部与虚部曲线及纵、横剖面。结果表明,与场源平行的剖面上倾子响应的振幅、实部与虚部对地下横向不均匀异常体边界反演灵敏,能够有效反应出地下电性异常体重要信息,并且能够正确的与正演模型相吻合;倾子响应横切片图中表明,倾子相位能够显示地下电性异常体的位置,并能够很好的确定异常体的中心;研究不同频率条件下,地下电性异常体的倾子响应特征,发现倾子资料具有测深的功能。可见可控源电磁法倾子资料能够用于地下地质构造的解释,并能准确划分异常体边界的确定中心位置。说明可控源倾子电磁法有着很好的理论基础,具有良好的应用前景。

The Study of Three-dimensional Forward for the Tipper Response of the Controlled Source Electromagnetic Method

In order to overcome the disadvantages of the weakness signal of the components of magnetic field in magnetotelluric(MT), easily to be disturbed by electromagnetic(EM) noises, and the tipper was difficult to be calculated, the data for observation, processing and interpretation of the controlled source electromagnetic (CSEM) tipper method were used to investigate in this paper. By means of three-dimensional CSEM forward modeling, three components of magnetic field were calculated. The curves and orthogonal profiles of tipper amplitude, phase, real and imaginary over anomalous body were drawn to used as feature analysis, the results show that the amplitude, real and imaginary of tipper on the profile parallel to the source are very sensitive to the boundary of the anomalous body, and exhibit more important information to the body, which are correspond to the forward model. From the slices of the amplitude, phase, real and imaginary of tipper at different frequencies the position of body can be identified easily. The different features at different frequencies show that the tipper can be used for sounding. All of which can be used to confirm that the tipper data can be used for the interpretation of underground geological structures, so that the boundaries and the center of body can be identified. It is concluded that the controlled source electromagnetic tipper has a firm foundation of EM theory, and shows a good prospect in electrical exploration.