Abstract Non-invasive geophysical techniques employed across the Himalayan Frontal Thrust (HFT) at Singhauli in the north-western Frontal Himalaya to understand shallow subsurface geological structures and their nature in the context of active tectonics. The combination of high-resolution Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Multi-channel Analysis of Surface Waves (MASW) techniques with the different acquisition parameters found to be beneficial in gaining high-resolution images of shallow subsurface geological structures. The contact zone of resistivity obtained between 134 Ωm suggests the juxtaposition of dissimilar lithological units explained as two faults dipping to the northwest related to the HFT. The average separation between Fault 0 and Fault I is 12m which in general agreement with the trench excavation survey. The GPR radargram over a length of 45m show offset reflectors at a horizontal distance of ∼12–15m close to the active deformation zone. The horizontal reflectors abruptly truncate across two northerly dipping planes. The 2D Vs section (MASW1&2) exhibited dipping attitude of the litho units (with different velocity zones) in the northeast direction which are also consistent with the local geological setting. Prominent liquefaction feature identified in the ERT section specifically with the 1 and 1.5m electrode spacing show explicit expression of its existence due to contrasting resistivity ranging between 100 and 450 Ωm. A strong correlation has been established between the field based geological observations, carried out earlier in this area through a trench excavation survey, with the present work using geophysical techniques. The integrated approach found to be highly beneficial in those areas where contrasting sub lithological units exist in terms of their physical properties. This study argues for judicious use of the ERT, GPR and MASW techniques to delineate shallow subsurface geology across various active faults in the Himalayan terrain to comprehend the active deformation related to large magnitude paleoearthquakes and earthquake hazard assessment.

中文翻译：

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印度 Ka​​la Amb Singhauli 喜马拉雅前冲断层活动变形地下成像综合地球物理技术

摘要 在喜马拉雅西北部 Singhauli 的喜马拉雅锋冲断层 (HFT) 上采用非侵入性地球物理技术，以了解活动构造背景下的浅层地下地质结构及其性质。高分辨率探地雷达 (GPR)、电阻率层析成像 (ERT) 和表面波多通道分析 (MASW) 技术与不同采集参数的结合被发现有助于获得浅层地下地质的高分辨率图像结构。在 134 Ωm 之间获得的电阻率接触带表明不同岩性单元的并置被解释为与 HFT 相关的两个向西北倾斜的断层。断层 0 和断层 I 之间的平均间隔为 12m，与沟渠开挖调查基本一致。长度为 45m 的 GPR 雷达图显示了靠近活动变形区的水平距离约 12-15m 处的偏移反射器。水平反射体在两个北倾平面上突然截断。二维 Vs 剖面（MASW1&2）表现出东北方向岩性单元（不同速度带）的倾斜姿态，这也与当地地质背景一致。由于 100 和 450 Ωm 之间的电阻率对比，在 ERT 部分中识别的突出液化特征特别是 1 和 1.5m 的电极间距显示了其存在的明确表达。野外地质观测之间建立了很强的相关性，早些时候通过沟渠挖掘调查在该地区进行，目前的工作使用地球物理技术。综合方法被发现在那些在物理性质方面存在对比亚岩性单元的地区非常有益。本研究主张明智地使用 ERT、GPR 和 MASW 技术来描绘喜马拉雅地形中各种活动断层的浅层地下地质，以了解与大规模古地震和地震危害评估相关的活动变形。