Characterization of Subsurface Cracks with Polarimetric Borehole Radar

利用偏振钻孔雷达表征地下裂纹

• 批准号: 07555326
• 负责人: NIITSUMA Hiroaki
• 金额: $ 11.39万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07555326/
• 关键词: Radar Polarimetry; Polarimetric radar; Borehole Radar; Ground Penetrating Radar; Fault Survey; Nojima Fault; Subsurface Crack Measurement; レ-グポラリメトリ

(Polarimetric Borehole Radar Sstem)We developed borehole a radar system which is capable of radar polarimetric measurement in boreholes. The system uses the combination of dipole antennas and slot antennas to control the transmitter and the receiver polarimetry. The aim of the polarimetric radar measurement includes characterization of geological properties of anomalies such as the roughness of the subsurface cracks and geological boundaries.(Field Measurement)Field experimental results in a borehole in Awaji Island, which was drilled to investigate the natural fault caused the Kobe earthquake in 1995 was discussed. In this measurement, co-polarization reflection and cross-polarization reflection were measured at the same depth with two different combinations of antennas. The material is granite and has frequent fractured zones. The Nojima fault, which caused the Kobe earth quake was observed below 1500m in this borehole. The polarimetric radar measurement was carried out in the section between 1000 and 1052m. The radar profile corresponds well to the other data such as electrical logging and BHTV (Ultra sonic imaging).(Radar Polarimetry)The difference of reflectivity depending on the polarization was also observed in this measurement was discussed. Reflected signal from single fractures is polarized in one direction, however, those from fractured zones are randomly polarized. Theses information could not be obtained with conventional radar measurement and will be a important tool for characterization of subsurface cracks.

我们研制了一种钻孔雷达系统，它能够在钻孔中进行雷达极化测量。该系统使用偶极子天线和缝隙天线的组合来控制发射机和接收机的极化。偏振雷达测量的目的包括表征异常的地质特性，例如地下裂缝和地质边界的粗糙度。（现场测量）讨论了1995年科比地震中为调查天然断层而在淡路岛钻孔的现场实验结果。在该测量中，共极化反射和交叉极化反射在同一深度处用两种不同的天线组合测量。材料为花岗岩，经常有断裂带。在该钻孔中，观测到了1500米以下的野岛断层，该断层曾引起科比地震。在1000 ~ 1052 m的剖面上进行了极化雷达测量。雷达剖面与电测、超声波成像等资料吻合较好。本文还讨论了反射率随偏振态的变化规律。单裂隙反射信号偏振方向单一，而裂隙带反射信号偏振方向随机。这些信息无法获得与传统的雷达测量，将是一个重要的工具，表征地下裂纹。

项目成果

M. Sato, T. Miwa and H. Nitsuma: "Polarimetric Borehole Radar for Fracture Evaluation" VIII Int.Symp on the Observation of the Continental Crust Threugh Prilling. (1996)

M. Sato、T. Miwa 和​​ H. Nitsuma：“用于裂缝评估的极化钻孔雷达”VIII Int.Symp 通过造粒观测大陆地壳。

佐藤 源之: "地中レーダ技術" セメント・コンクリート. 593. 1-8 (1996)

佐藤元之：“探地雷达技术”水泥/混凝土。 593. 1-8 (1996)

T. Miwa, M. Sato and H. Niitsuma: "Rough Surface Anisotropy Estimation by Wideband Polarimetric Borehole Radar" Proc. of the 1996 Int. Symposium on Antennas and Propagation. 1065-1068 (1996)

T. Miwa、M. Sato 和 H. Niitsuma：“通过宽带偏振钻孔雷达进行粗糙表面各向异性估计”Proc。

M.Sato: "Ground penetrating radar technology (in Japanese)" Cement/Concrete. 593. 1-8 (1996)

M.Sato：“探地雷达技术（日语）”水泥/混凝土。

T.Miwa, M.Sato and H.Niitsuma: "Rough Surface Anisotropy Estimation by Wideband Polarimetric Borehole Rader" Proc.of the 1996 Int.Symposium on Antennas and Propagation. 1065-1068 (1996)

T.Miwa、M.Sato 和 H.Niitsuma：“通过宽带偏振钻孔雷达进行粗糙表面各向异性估计”Proc.of 1996 Int.Symposium on Antennas and Propagation。