摘要:
对瞬变电磁法 (TEM)测量数据作波场变换,可以实现TEM数据的拟地震成像解释,其中,虚拟波动场波形展宽现象是阻碍这一应用的关键问题。本文采用Tikhonov正则化算法和选取正则因子的L准则,对具有解析结果的波场变换方程进行了数值求解。数值计算表明,由于数值计算引入的展宽是虚拟波动场波形展宽的主要因素,因此,减小数值求解波场变换方程时所引入的波形展宽,应当是波场变换方程应用研究的重要问题之一。
Abstract:
By the wavefield transformation, which can transform the diffusive electromagnetic fields to wavefields defined in a time-like variable mathematically, if the corresponding wavefields can be accurately computed from the transient electromagnetic (TEM) sounding data, one would be able to interpret these TEM data using techniques developed for the wavefields such as the seismic migration imaging. In this paper, the Tikhonov regularization method and the L-curve criterion for determing the regularization factor has been adopted to solve an analytical wavefield transformation pair. From our numerical results, we find that, although above method can give us some regularized results correctly, but it also can severely introduce waveform broadening phenomena “numerically" with increasing the observer offset and the conductivity of earth that will severely reduce the imaging resolution in engineering. So, developing a numerical method that can reduce the transformed waveform broadening phenomena is the key issue to apply the wavefield transformation in addition to migration imaging technique interpreting the TEM sounding data.
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