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.

（极化钻孔雷达系统）我们开发了钻孔雷达系统，能够在钻孔中进行雷达极化测量。该系统使用偶极天线和缝隙天线的组合来控制发射机和接收机的极化测量。偏振雷达测量的目的包括表征异常的地质特性，例如地下裂缝的粗糙度和地质边界。（现场测量）淡路岛钻孔的现场实验结果，该钻孔是为了调查导致地震的自然断层而钻探的。讨论了1995年的神户地震。在本次测量中，使用两种不同的天线组合在同一深度测量同极化反射和交叉极化反射。该材料是花岗岩，具有频繁的断裂带。在该钻孔中观测到导致神户地震的野岛断层位于1500m以下。极化雷达测量在1000～1052m区间进行。雷达剖面与电测井和 BHTV（超声波成像）等其他数据很好地对应。（雷达偏振测量）在该测量中还观察到反射率随偏振的差异。来自单个裂缝的反射信号是沿一个方向偏振的，而来自裂缝区域的反射信号是随机偏振的。这些信息无法通过常规雷达测量获得，将成为表征地下裂纹的重要工具。

项目成果

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)

M.Sato, T.Miwa and H.Niitsuma: "Polarimetric Borehole Rader" Proc.of Progress in Electromagnetics Research Symposium. 80 (1996)

M.Sato、T.Miwa 和​​ H.Niitsuma：“极化钻孔雷达”Proc.of 电磁学研究进展研讨会。

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。

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。

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。