3-D Inversion Algorithm for Surface-Tunnel Controlled-Source Electromagnetic Data

可控源电磁法是一种重要的地球物理勘探方法，也是金属矿等战略性矿产资源的勘查的重要方法之一。常规的可控源电磁法通常采用地面发射–地面接收的观测装置，在一定程度上限制了其勘探深度。若使用地面发射–巷道接收的观测装置，在离地下目标体更近的巷道采集数据，有望提升对深部结构的探测能力。然而，当前地–巷可控源电磁法鲜有研究，为研究地–巷可控源电磁法的可行性和勘探效果，文章首先开发了地–巷可控源电磁三维反演算法，然后设计了理论地–巷勘探模型，对该模型进行了反演测试，结果表明，联合反演地面–巷道数据可有效提升可控源电磁法的深部探测分辨率，为地–巷可控源电磁法的实际应用提供了理论参考和依据。Controlled-source electromagnetic (CSEM) method is a crucial geophysical exploration technique and plays a significant role in the exploration of strategic mineral resources such as metal ores. Conventional CSEM typically employs a surface transmitter-surface receiver configuration, which, to some extent, limits its exploration depth. By adopting a surface transmitter-underground tunnel receiver configuration, where data are collected in tunnels closer to underground targets, the detection capability for deep structures can potentially be enhanced. However, research on surface-tunnel CSEM remains scarce. To investigate the feasibility and exploration effectiveness of surface-tunnel CSEM, this paper first develops a 3D inversion algorithm for surface-tunnel CSEM. Subsequently, a theoretical surface-tunnel exploration model is designed, and inversion tests are conducted on this model. The results demonstrate that joint inversion of surface-tunnel data can effectively improve the resolution of CSEM for deep exploration, providing theoretical references and a foundation for the practical application of surface-tunnel CSEM.