大地电磁资料精细处理和二维反演解释技术研究(五)——利用阻抗张量成像识别大地线性构造

大地线性构造往往与块体或物性的边界、断裂的几何延伸相关联,是地学研究的重要目标构造.在大地电磁法中,传统的方法是通过反演得到的电性结构的差异来解译线性构造,是一种间接分析方法.由于线性构造发育处走向和倾向明显,二维性较其他地方一般会更强,故而在阻抗张量成像分析中,相应的二维有效因子就会比较大,最佳主轴统计分布会更加明显.据此,本文利用大地电磁阻抗张量成像(包括最佳主轴统计成像、构造维性成像)来探测识别大地线性构造.本文首先通过三维理论模型的研究结果来验证这一技术在线性结构探测中的有效性,然后将其应用于郯庐断裂带南段实测剖面的具体分析中,展示了这一技术在线性构造探测中的实用性及其数据处理与分析过程.本文研究表明,大地电磁阻抗张量成像技术可独立于反演为地质解释尤其是线性构造的解释提供诸多参考信息.

Refined techniques for data processing and two-dimensional inversion in magnetotelluric (V): Detecting the linear structures of the Earth by impedance tensor imaging

The linear structure of the earth is often associated with the boundary of the block or physical property and the geometric extension of faults, which is an important target structure of geo-science research. In the magnetotelluric method, the usual method is to interpret the linear structure by the difference of the electrical structure obtained by the inversion, which is an indirect analysis method. For the region rich of the linear tectonic structure, the strike or the dip is more obvious, the two-dimensionality is more stronger than other places. So in the impedance tensor imaging analysis, the corresponding two-dimensional effective factor will be larger, and the statistical distribution of the geo-electrical strike will be more obvious. Based on this, the magnetotelluric impedance tensor imaging (including the optimal principal azimuth statistical imaging and the structural dimension imaging) is used to detect and identify the linear structure of the earth. In this paper, the validity of the technique in the linear structure detection is verified by the research results of the three-dimensional theoretical model, and then applied to the field data analysis of the southern section of the Tan-Lu fault zone. Through these examples, we show the data processing and analysis of this technique using in detecting and identifying the linear structure. This study shows that the magnetotelluric impedance tensor imaging technique can provide rich reference information for geological interpretation, especially the interpretation of linear structure, independent of the inversion result.