On the study of electromagnetic prospecting using holographic imaging

研究了全息成像技术在高分辨率电磁勘探中的应用。我一直在研究近场全息理论对时间域电磁方法的适用性。传统全息术的分辨率取决于波长，并且与波长的分辨率相同。但是，近场全息术的分辨率与波长无关，希望小于波长的1/1000。高分辨率勘探意味着获得高精度的数据。为了提高测量的分辨率，应提高时间域电磁法的精度，这是一种野外数据获取方法。研究了时间域法的特点，比较了其他电磁法和三维建模的时间域数据，频域法和大地电磁法一样，如果地表有低阻层，对深部异常的响应往往较小。它的探测深度往往比电磁波的皮肤深度小得多，后者通常是用频域数据的探测深度估计的。在时间域上，只有在较长时间内获得稳定的数据，才会有较长的响应时间，表面低阻层的影响较小。我研究了三维结构对二维(电阻率结构垂直于剖面均匀)假设下的电阻率模型的影响。位于剖面旁、浅层的异常突出于二维剖面的深部。这种投影在时间域中也出现了类似的情况，我们应该发展三维全息模型来避免这种影响。

The study was carried out to investigate the applicability of holographic imaging to the high resolution electromagnetic prospecting. I have been studying an applicability of the near-field holography theory to the time domain electromagnetic method. Resolution of the conventional holography depends on the wave length and is expected to same order of it. But, resolution of the near field holography does not relate to the wave length and is expected to less than 1/1000 of it.A high resolution prospecting means obtaining high accurate data. We should increase accuracy of time domain electromagnetic method, which is one for obtaining the data in a field, to increase resolution of the survey. I have been studying feature of the time domain method comparing other electromagnetic method and three dimensional modeling of the time domain data.A frequency domain method, like magnetotelluric method, tend to show less response to an anomaly at depth if low resistivity layer is situating at the surface. The depth of investigation of it tend to be much less than the skin depth of electromagnetic wave, which is usually using estimation of depth of investigation for frequency domain data. In time domain, the response time is only longer and the effect of low resistive layer at surface is less if the data obtain stably during the longer time.I have investigated an effect of three dimensional structure on the resistivity model assumed two dimensional (resistivity structure is uniform at vertical to the section). The anomaly situated beside the section and at the shallower depth is projecting at the deeper part of the two dimensional section. The projection appears in the time domain case similarly and we should develop three dimensional holographic modeling to avoid such effect.