隐伏断裂构造音频大地电磁法探测

Exploration of Concealed Fault Structures in Audio Magnetotelluric Method (AMT)

音频大地电磁法由于其具有探测深度大、横向分辨率高、不受低阻屏蔽效应影响等技术优势,近年来在解决大深度地质问题中得到了较为广泛的应用。隐伏断层由于其潜伏在地表以下一定深度,并且构造走向不确定,增加了探测的难度。采用音频大地电磁法探测观测区隐伏断裂构造,基于可以对数据进行构造走向分析,首先确定观测区构造走向,为北西45°为主,然后对观测数据进行阻抗张量旋转,采用非线性共轭梯度反演方法对旋转后的数据进行二维反演,得到观测区二维电性结构。结果表明,音频大地电磁法可以有效探测隐伏断裂构造的空间分布特征。

The audio magnetotelluric method（AMT）,with the advantages of large detection depth,high transverse resolution,not affected by the low resistance shielding effect,has been widely used in solving the deep geological problems in recent years.The concealed fault has a certain depth below the surface and the uncertainty of tectonic trend increases the difficulty of detection.In this paper,the audio magnetotelluric method is used to detect the concealed fault structure in the observation area.Based on the analysis of the tectonic trend from the data,firstly,the tectonic trend of the observation area is determined,which is mainly in the north-west 45°,then the impedance tensor rotation of observed data is carried out,and the inversion method of nonlinear conjugate gradient is used to inverse therotated data in order to obtain the two-dimensional electrical structure in the observed area.The results show that the audio magnetotelluric method can effectively detect the spatial distribution of concealed fault structures.