频率域可控源电磁法2.5D正反演

2.5D forward and inversion of CSEM in frequency domain

CSEM有MT不可比拟的优势,得到国内外学者多年的大力发展,但是,其数据处理水平尚停留在1D和2D近似解释阶段。2.5D相对来说更加符合实际情况(3D),要想进一步发展该方法,必须开展CSEM 2.5D或3D正演和反演研究。采用有限元法实现了CSEM 2.5D正演模拟,在验证其代码有效的前提下,计算了水平地形和地堑地形的电磁场响应。采用共轭梯度法实现了对场值直接进行反演的算法。从试算低阻和高阻模型的结果可知,反演算法精度高,计算速度快,初步达到了实用化的程度。

CSEM is superior to MT to some extent. Plenty of scholars all over the world are developing this exploration method, while the level of processing CSEM data is still staying on 1D and 2D approximate inversion approaches. 2.5D modeling can better simulate the true earth than the 1D and 2D modeling. In order to enhance application of this method, 2.5D or 3D forward and inversion algorithm should be developed. Adopting the finite element method represents CSEM 2.5D modeling. After evaluating the accuracy of the forward code, the electromagnetic responses of one horizontal model and one topography model were calculated. Finally, the conjugate gradient method was used to complete the field inversion algorithm. From the outcomes of response inversion, this inversion approach not only has high precision, but also has a very fast calculation speed. So the inversion code can be used into production.