Inter-borehole electrical resistivity imaging of englacial drainage
Inter-borehole electrical resistivity imaging of englacial drainage
复制标题
冰川排水孔间电阻率成像
DOI：
10.3189/s0022143000002756
复制
发表时间：
1998
影响因子：
3.4
通讯作者：
B. Kulessa
中科院分区：
文献类型：
--
作者：
B. Hubbard;A. Binley;L. Slater;R. Middleton;B. Kulessa
基于钻孔的电阻率测量能够增强我们对温带冰中冰川排水通道结构的理解。我们总结了目前在水文地质调查中使用的井间电阻率层析成像（ERT），并适用于成像冰川排水。在瑞士Haut glacier d’arolla对钻孔水进行人工矿化后，ERT连接首次在冰川冰中成功进行。在这里，两种类型的电气连接在间距达10米的井眼之间进行，钻至20至60米的深度。大多数测试表明存在电阻性均匀冰，均匀体电阻率为~108 - 109 Ω m。然而，ERT也成功地用于识别和表征冰川表面以下~ 13 m处两个钻孔相交的水力导电性冰川裂缝。钻井记录表明存在这种连接空洞，并通过双井眼冲击测试进行了验证。这些钻孔的重建层析图特征为~109 Ω m的背景冰电阻率场，在~13 m的深度被一个尖锐的亚水平低电阻率带（~ 104 Ω m）破坏。因此，井间ERT具有对均匀和断裂的温带冰川冰成像的能力。
Abstract Borehole-based electrical resistivity surveys have the capacity to enhance our understanding of the structure of englacial drainage pathways in temperate ice. We summarize inter-borehole electrical resistivity tomography (ERT) as currently used in hydrogeological investigations and as adapted for imaging englacial drainage. ERT connections were successfully made for the first time in glacier ice, following artificial mineralization of borehole waters at Haut Glacier d’Arolla, Switzerland. Here, two types of electrical connection were made between boreholes spaced up to 10 m apart and drilled to depths of between 20 and 60 m. Most tests indicated the presence of resistively homogeneous ice with uniform bulk resistivities of ~108 - 109 Ω m. However, ERT was also successfully used to identify and characterize a hydraulically conductive englacial fracture that intersected two boreholes at a depth of ~ 13 m below the glacier surface. The presence of this connecting void was suggested by drilling records and verified by dual borehole-impulse testing. The reconstructed tomogram for these boreholes is characterized by a background ice-resistivity field of ~109 Ω m that is disrupted at a depth of ~13 m by a sharp, sub-horizontal low-resistivity zone (~10 4 Ω m). Inter-borehole ERT, therefore, has the capacity to image both uniform and fractured temperate glacier ice.