大地电磁测深数据处理方法技术进展
Technical progress of processing methods for magnetotelluric sounding data
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摘要: 大地电磁测深法以其探测深度大、不受高阻层屏蔽、设备轻便、成本低等优势,被广泛用于地球动力学、成矿系统等研究以及深部资源和(清洁)能源探测、灾害调查等领域。然而,该方法在观测天然电磁场信号方面信号较弱,容易受到噪声干扰,一般需长时间观测和多次叠加方式来获取电性信息,且需同时开展相应的数据处理和分析,以获得更为可靠的地下电性结构。其中,数据处理一般包括时频转换、去噪、阻抗张量和倾子矢量估计,数据分析主要包括电性主轴和介质维度分析。基于前人关于大地电磁测深探测方法的研究成果,针对探测体系中处理、分析的关键环节,总结目前普遍使用的方法,并基于数据处理中的去噪、数据分析中的阻抗和相位张量,介绍探测体系中重要环节的前沿研究方向和成果,分析现有方法各自的特点和优点及其在不同环境和背景下大地电磁场观测数据的适用性,为大地电磁测深的有效、高效应用提供理论信息和基础保障。Abstract: The magnetotelluric sounding method is widely used in researches on geodynamics, metallogenic system, deep exploration of mineral resource and clean/oil energy and investigation of geological disaster, due to its advantages of large detection depth, penetrating high resistance layers, portable performance and low cost. However, the performance of this method is weak in natural electromagnetic field signals observation, which is easily interfered by noise. The effective electrical information is obtained by long-term observation and multiple superposition, and the related data processing and analysis methods were used to obtain reliable geo-electrical results. Data processing usually includes time-frequency conversion, denoising, estimation of impedance tensor and tipper vector, and data analysis includes electrical strike direction and medium dimension analysis. In this paper, the authors summarized the widely used processing methods for magnetotelluric sounding data, based on previous research and introduced the forefront research directions and achievements focusing on denoising in data processing and impedance and phase tensor in data analysis. The characteristics and advantages of the existing methods, and the applicability to geomagnetic field observation data under different environments and backgrounds were analyzed to provide theorical information and basic guarantee for effective and efficient application of magnetotelluric sounding.