3D Electrical Resistivity Tomography of Karstified Formations Using Cross-Line Measurements

Abstract

19The acquisition of a full 3D survey on a large area of investigation is difficult, and from a 20 practitioner's point of view very costly. In high-resolution 3D surveys, the number of electrodes 21 increases rapidly and the total number of electrode combinations becomes very large. In this 22 paper, we propose an innovative 3D acquisition procedure based on the roll-along technique. It 23 makes use of 2D parallel lines with additional cross-line measurements. However, in order to 24 increase the number of directions represented in the data, we propose to use cross-line 25 measurements in several directions. Those cross-line measurements are based on dipole-dipole 26 configurations as commonly used in cross-borehole surveys. We illustrate the method by 27 investigating the subsurface geometry in a karstic environment for a future wind turbine project. 28We first test our methodology with a numerical benchmark using a synthetic model. Then, we given its sensitivity to electrical resistivity, where the 3D nature of the dissolution processes 72 makes the 2.5D hypothesis of the subsurface much weaker than for fault imaging for example. 73In most cases, the acquisition of a full 3D survey on a large area of investigation is difficult and, 74from a practitioner's point of view, very costly. In high-resolution 3D surveys, the number of 75 electrodes increases rapidly and the total number of electrode combinations becomes very large. 76Even with multi-channel acquisition systems, the time to acquire a complete data set is 77 prohibitive and even impossible as most systems can only handle a limited number of electrodes, 78and only through costly extensions to the main unit. In most applications, 3D surveys with a 79 substantial number of electrodes (more than 100) are not full 3D informative surveys but limit 80 the directions in which data is acquired to the two main directions and the cross-diagonal (e.g.,

Hydrogeophysical modelling of Hisarcik (Kütahya) geothermal field, western Turkey

“…; Van Hoorde et al . ). The low resistive anomaly can be further enhanced in the case of the presence of hot water in the thermal springs seeping through the faults.…”

Shallow geophysical and hydrological investigations to identify groundwater contamination in Wadi Bani Malik dam area Jeddah, Saudi Arabia

“…Electrical resistivity profiling (ERP) provides valuable information on resistivity of subsurface material which will be used to create 2D and 3D resistivity models. The variation in resistivity values provides probable direction of landfill leachate flow in subsurface [10][11][12][13][14].…”