【作者】 朱宏伟；

【导师】 李貅；

【作者基本信息】 长安大学 ， 地球探测与信息技术， 2009， 硕士

【摘要】 地球物理研究中有很多不适定问题,解决起来有很大困难,电磁法勘探中这种现象尤为突出。在瞬变电磁法中传统上是用经典的电阻率公式算出地下电阻率分布情况。但要得到地下电性分界面则很难从中区分,因为传统成像图中的电阻率分布是渐变的。如果换成对电性界面表现更好形象的波动方程,并在此过程中移植地震勘探中的诸多成熟技术,则会大大提高分辨能力,进而对提高勘探精度有很大帮助。如今在瞬变电磁场中,学术界已寻找到一个数学上的处理办法,即利用现有瞬变电磁场变换成“波场”。在已解决波场逆变换问题的基础之上,将原满足扩散方程的瞬变电磁场变换为波场来处理。运用克希霍夫积分,将虚拟地震波场由地面向地下反向逆时偏移成像。把波场分析的原理用于对瞬变电磁场的解释,就形成了瞬变电磁偏移方法。从波场角度看,它拓展和丰富了瞬变电磁场的内涵,以前用常规解释方法处理实测资料无法提取的信息,在利用上述方法对地下目标体直接成像后,变得更加容易得到。在此过程中,扩散场刚转化为波场后,为使得波形在“强”“弱”反射面的振幅有可比性,需要求取均衡系数以方便后期成像处理;为抵消大地滤波作用,对电性界面精确定位,可以通过对虚拟波场的离散数据求取反褶积,以达到“锐化”反射面的效果;然后,同样基于为得到良好成像效果之目的,利用多点平滑处理波形。如此,在延拓成像中即可更精确的确定界面深度。取得的一些结论,将为在瞬变电磁法中正确合理地引入地震处理解释方法提供重要的理论依据,和实验参照。更多还原

【Abstract】 There’re many of ill-posedness problems in geophysical research, for that, we can hardly handle them most of the time, especially in the electromagnetic exploration method. Tranditionally, the data of resistivity under groud are usually calculated with the classical resistivity formula in the field of TEM. At the same time, to get the depth of interface of the resistivity are not easy, because the data are gradual changed at the chart of resistivity profile. It will be inproved on the sharpness of ’ separation and be great helped on exploration precision, if it can be change to the form that could expressed by wave equation ,which have the power to show the interface, since for doing that, lots of mature technology belonged to seismic exploration will be introduced into TEM.Nowadays, a math treatment has been found in academe group that is to transform to wave field from the TEM data. Base on the wave field inverse transformation problem, which has been solved, in TEM, we can turn diffusion to wave for better deal with. The seismic wave field is migrated imaging from earth surface to underground opposite to general, with Kirchhoff integral method, in doing this, migration method will be made in TEM if we use the wave field analysis principle. In the view of the wave field that extends the connotation of TEM electromagnetic field, and makes the information unfold that was covered before. We are able to get the signal more easily when imaging directly.After getting the wave field from diffuse field, to balance two kinds of plane of reflection, both strong and weak, the equilibrium coefficient’s computing is needed that’s for post treatment. The deconvolution should be calculated with virtual wave field discrete data, for reaction the interface accurately, as the effect of earth filter. After that for the sake of the same purpose, multiple point smoothing should be use in our wave shape, just for better outcome. The conclusions we get are going to be provided to theoretical basis and experimental reference, for that seismic data processing utilizing to TEM reasonably.更多还原