地质雷达在乌拉山山前断裂探测中的应用

地质雷达是利用电磁波对地下不同电性介质进行探测的地球物理仪器,其探测速率快、分辨率高,可弥补探槽和其他地球物理方法存在探测盲区的缺陷,正在越来越多地应用于活动断层探测领域。本文以乌拉山山前断裂为例开展地质雷达探测工作,使用无人机正射影像技术对测线进行地形校正,获得断层浅部地质雷达图像。研究结果表明,本文研究方法能有效反映探槽揭露的地层单元和断层分布。本次探测中,雷达波形图像特征为:浅地表的土壤层反射波总体较弱;粗粒沉积为主的砾石层反射波总体较强,同相轴连续性好;细粒沉积为主的砂层反射波弱于砾石层,波形以中、高频为主,同相轴具有弱连续性;对于洪冲积地区,地质雷达能分辨具有一定特征的地层单元,这为剖面图像的断层识别提供了标志;通过无人机正射影像技术对地质雷达测线进行地形校正,有利于获得更为准确的探测结果。

Application of Ground Penetrating Radar in Fault Detection of the Wulashan Piedmont Fault

Ground Penetrating Radar(GPR) detection is a geophysical method which uses electromagnetic wave to detect different electrical media underground. Because of its fast detection rate and high resolution, it can make up the blind spot between the exploration trough and other geophysical methods, and is increasingly applied in the field of active fault detection. This paper takes the Wulashan Piedmont Fault as an example to carry out the detection test. We use the uav orthophotography technology to conduct terrain correction on the survey line, and obtains the shallow fault GPR image. Finally, the detection results were compared with existing trenches. After comparison, we find the radar image can effectively reflect the faults and stratigraphic units that exposed by the trenches.The GPR image shows the following characteristics:the reflection in the soil layer is generally weak; in the sand and gravel layer, the overall reflection is strong, the low-frequency component is prominent, and the in-phase axis continuity is good. The reflection in sand layer is weaker than that in gravel layer, and the waveforms are mainly medium and high frequency. Therefore, for the flood alluvial area, the GPR can distinguish the stratigraphic units with certain characteristics, which provides a marker for the fault identification of profile image. At the same time, the uav orthophoto image technology can realize terrain correction of GPR survey line.