中小收发距CSAMT在浅层地球物理勘查中的应用

摘要

通过分析双极源在均匀半空间表面电磁场平面分布特征和探讨收发距对最大探测深度的制约关系，认为小收发距、长供电极距、短测量极距的CSAMT装置可以应用于强干扰环境下浅层地球物理勘查，并具有信噪比高、沿测线方向电磁场分布均匀的优点。简要介绍野外工作方式和数据处理方法，列举人文干扰环境下典型实测曲线、偶极－偶极电阻率测深对比试验以及浅层勘查应用实例。对比试验反演结果对应关系较好，但CSAMT有施工便利、分辨率高、抗干扰能力强的优势；应用实例推断结果与钻孔验证情况吻合，表明中小收发距CSAMT在浅层地球物理勘查中有实用价值和应用前景。%Based on analyzing the excitation distribution characteristics of the bipolar source in a homogeneous half⁃space electromag⁃netic field and discussing the correlation between the transmit⁃receive distance and the maximum depth of prospecting, the authors hold that CSAMT characterized by small transmit⁃receive distance, long bipolar source and short potential electrodes can be applied to geo⁃logical exploration in the shallow layer of a strong noisy⁃level environment, and has such merits as high signal⁃to⁃noise and uniform dis⁃tribution of electromagnetic field along the line direction. This paper briefly describes fieldwork and data⁃processing methods of CSAMT, and illustrates typical experimental curves under man⁃made interferences, controlled tests on the dipole⁃dipole resistivity sounding and applied cases in shallow geophysical exploration. The inversion results are similar in controlled tests, but CSAMT has higher resolution and stronger anti⁃interference capability. Interpretations of applied cases match the drilling verification, indicating that CSAMT with small and medium⁃sized transmit⁃receive distance array has practical value and application prospect in the shallow geo⁃physical exploration.