Development and Application of a Variable-Frequency-Based Electric Sounding System for Increasing the Accuracy of Aquifer Detection

Introduction to the Special Issue on the ISME-XV: Toward Sustainable Society with Natural Resources—Development of Resource Exploration Technology in the Past Thirty Years and for the Future

“…The ninth paper, by Asaue et al (2021), presents a development of a variable frequency-based electric sounding system (VFES), to increase the accuracy of detecting aquifers by measuring apparent resistivity in the frequency range 1-100 Hz at intervals of 1 Hz. The paper demonstrates the effectiveness of VFES in soil-water sample and aquifer-model experiments and in three field experiments with different geologic settings by using the coefficient of variation (C v ) of the resistivity in the frequency range 21-40 Hz.…”