| Co-Investigator(Kenkyū-buntansha) |
周 輝 東北大学, 東北アジア研究センター, 講師(研究機関研究員)
EBIHARA Satoshi Center for Northeast Asian Studies, Tohoku University, Research Associate, 東北アジア研究センター, 助手 (20301046)
ZHOU Hui Center for Northeast Asian Studies, Tohoku University, Part-timer Researcher
|
|---|
| Research Abstract |
Polarimetric borehole radar has a good potential for detecting and evaluating radar targets beyond the radar resolution determined by the wavelength. This is a great advantage for borehole radar, which is often used I lossy subsurface material. In this research project, we have developed a polarimetric borehole radar system which operates under 200MHz, and can be installed in boreholes having a diameter less than 5cm.
In order to have a thin down hole sonde, we have developed a optical analog signal link which is equipped in a cylindrical casing of 2cm in diameter. The completed polarimetric borehole radar system has a diameter of 41 mm. This system was evaluated in field test and could show it can acquire polarimetric radar signal. At the same time, we found that the signal acquired by borehole radar, whose diameter is much smaller than that of a borehole is unstable, and we need additional equipment to set the down hole sonde at the center of the borehole.
Polarimetric borehole radar measurements were carried out in several test sites including Mirror Lake, USA, Asse, Germany and Hirabayashi, Japan. We showed that he full-polarimetric borehole radar profiles can be used for classification of subsurface fractures. Under certain conditions, we found that the water permeability is related to the surface roughness of the subsurface fractures, and the polarimetric borehole radar can evaluate them.
By using the cross-hole borehole radar measurement, we proposed a imaging technique based on migration. This technique can achieve higher resolution that the conventional tomography analysis.
|
