A three-dimensional transient electromagnetic data inversion method based on a time–frequency transformation  

作　　者：Yang Yun-Jian Wang Xu-Ben Liu Xue-Jun Mi Xiao-Li Mao Lifeng 

机构地区：[1]College of Geophysics,Chengdu University of Technology,Chengdu,Sichuan 610059,China [2]BGP Inc.,Zhuozhou 072750,China

出　　处：《Applied Geophysics》2020年第3期361-376,共16页应用地球物理（英文版）

基　　金：the National Key Research and Development Program of China(No.2016YFC060110403).

摘　　要：Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.

关 键 词：Transient electromagnetic method TEM digital filtering time-frequency transformation 3D EM forward 3D EM inversion 

分 类 号：P631.325[天文地球—地质矿产勘探]