Combining Electrical Resistivity Tomography and Ground Penetrating Radar to study geological structuring of karst Unsaturated Zone
Combining Electrical Resistivity Tomography and Ground Penetrating Radar to study geological structuring of karst Unsaturated Zone
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DOI：
10.1016/j.jappgeo.2013.03.014
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发表时间：
2013-07-01
影响因子：
2
通讯作者：
Emblanch, Christophe
中科院分区：
文献类型：
--
作者：
Carriere, Simon D.;Chalikakis, Konstantinos;Emblanch, Christophe
本文重点介绍了在典型的地中海土壤覆盖薄或无土壤覆盖的环境下，用一套简单的地球物理技术研究岩溶不饱和带（UZ）结构的有效性和互补性。二维探地雷达（GPR）和电阻率层析成像（ERT）这两种选定的技术在环境研究中得到了广泛的应用，许多科学家/工程师都可以使用它们。然而，单独的探地雷达或ERT无法提供喀斯特介质地质特征的增强表征。在本研究中，探地雷达结果提供了近地表高分辨率成像，从而可以提供地层和裂缝等相关地质信息。尽管结果很好，探地雷达的调查深度仍然限制在12米左右。ERT测量提供的视电阻率和反向电阻率显示出强烈的横向和纵向变化。这些变化可以告知一般的地质构造和特征方向。ERT能够探测到40米深的地层，但这是一种低分辨率的综合技术。在研究区域，所调查的石灰石是一种常见的电阻地层（超过2000欧米茄）。然而深度超过5-7米，ERT剖面显示了几个中等电阻率带（约900欧米茄）。在这些带中，地质探地雷达结果清楚地识别出与倾斜层理相对应的分层变化。探地雷达和ERT结果的结合可以提供一个完善的地质解释。这些具有倾斜层理的中等电阻率带可以解释低噪声地下实验室（LSBB）地下走廊内研究地点地表以下35 m处存在一个常年水流点。(C) 2013 Elsevier B.V.版权所有
This paper highlights the efficiency and complementarity of a light package of geophysical techniques to study the structure of karst Unsaturated Zone (UZ) in typical Mediterranean environment where soil cover is thin or absent. Both selected techniques, 2D Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT), are widely used in environmental studies and their application is accessible for a lot of scientists/engineers. However, GPR or ERT alone is not able to provide an enhanced characterization of geological features in karst media. In the present study, GPR results supply a near surface high resolution imaging and thus can provide relevant geological information such as stratifications and fractures. Despite the quality of the results GPR's investigation depth remains limited to around 12 m. Apparent and inverted resistivity provided by ERT surveys shows strong lateral and vertical variations. These variations can inform about general geological structuring and feature orientation. ERT is able to prospect down to 40 m but it's a low resolution integrative technique. In the study area the investigated limestone is a commonly electrical resistive formation (more than 2000 Omega.m). However deeper than 5-7 m, the ERT profiles reveal several zones of moderate resistivity (around 900 Omega.m). In these zones a stratification change corresponding to slanted bedding is clearly identified by GPR results. The combination of both GPR and ERT results can allow a well-established geological interpretation. These moderate resistivity zones with slanted beddings can explain the presence of a perennial water flow point 35 m below the surface of the studied site within the underground gallery of the Low-Noise Underground Laboratory (LSBB). (C) 2013 Elsevier B.V. All rights reserved.