Kirchhoff Integral Migration of Active Source EM Diffused Field for Stratified Media
As active source electromagnetic method, field data of Controlled Source Audio Frequency Magnetotelluric (CSAMT) method follow the wave diffusion equation. Propagating in solid earth media, diffusion electromagnetic (EM) signal has strong attenuation and dispersion comparing with seismic wave data, therefore the resolution power of CSAMT method is not better than that of seismic reflection method. However, there is consistence and similarity between EM signal and seismic wave in wave equation, we can apply Kirchhoff integral migration technique, a proven one in seismic method in time domain, to carry out pseudo-seismic processing for CSAMT signal in frequency domain so that the attenuation and dispersion can be made compensated in some extent, and the resolution power and interpretation precision of active EM wave hopefully can be improved.Considering that the EM wave satisfy the passive source homogeneous Helmholtz equation, we proceed EM wave with Green theorem and the active inhomogeneous Helmholtz equation, the Kirchhoff integral formula of EM wave can be derived. In practice, if we only consider the earth surface integral value, and assume that the intergral value in other interfaces is zero, we can only need the Green theorem in uniform half space, and then we can obtain frequency-domain Kirchhoff integral formula of EM wave in surface, which is also called downward migration of EM field in frequency domain. After taking the inverse Fourier transformation with reasonable image conditions and energy compensation,one can formulate the active source Kirchhoff integral migration expression for EM data in time domain.In this paper, we conducted EM field forward modeling and Kirchhoff migration for 4 typical stratified models with different frequency series,and different configurations between transmitter and reciever. Analyzing the EM properties,we can clarify near and far zone that can instruct us to carry out transmitter layout in practical application. Combined with field data surveyed in far zone, we perform Kirchhoff integral migration and compare the results with model to interpret.
Active source electromagnetic wave Diffused field Frequency domain Kirchhoff integral migration Stratified media
AN Zhiguo DI Qingyun WANG Miaoyue
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
国际会议
The 19th International Workshop on Electromagnetic Induction in the Earth(第十九届国际地球电磁感应学术研讨会)
北京
英文
526-530
2008-10-23（万方平台首次上网日期，不代表论文的发表时间）