可控源音频大地电磁法三维张量阻抗响应特征研究

Study on the characteristics of 3D CSAMT tensor impedance data

可控源音频大地电磁法(CSAMT)目前实际应用多以单个源采集标量数据为主,这种工作方式限制了CSAMT探测复杂地质构造的能力.随着CSAMT张量观测系统的推出和精细电法勘探的需求增多,CSAMT张量采集逐步受到重视.为了深化对CSAMT三维张量阻抗响应特征的认识,本文基于电场含源控制方程,采用交错网格有限差分法实现了CSAMT的三维正演算法;与二维CSAMT正演结果对比,验证了三维正演的正确性;设计了代表性三维地电模型,计算了标量和张量阻抗,对比和分析了标量和张量阻抗的响应特征.

CSCAMT is widely used and most of the researches have been carried out with scalar data acquisition system so far. It is the system using one single field source that has limited the ability of CSAMT to detect the complicated geological structures. Along with the development of the CSAMT data acquisition device and the increasing demands in precise and accurate electrical prospecting, lots of attention has been paid to CSAMT tensor acquisition pattern. In order to deepen our understanding of the characteristics of CSAMT tensor impedance, we have solved the CSAMT 3D forward problem through staggered-grid finite difference method based on the electric field control equation. A 2D model has been designed to test the validity and accuracy of the 3D forward algorithm. And then we have computed the scalar data and tensor impedance of a typical 3D model to analysis and compare the characteristics of two series of data. The advantage that the tensor impedance data shows demonstrates a new option for precise electric prospecting.