2016 Volume 84 Issue 1 Pages I_23-I_30
Determination of high salinity soil layers after leaching processes is required to safely resume farming in tsunami-affected regions. This study proposes a new method in which an electromagnetic induction sensor (EM38-MK2, Geonics) is used to determine the depth of the most saline layer. Based on a determination of horizontal spatial sensitivity of the EM38-MK2, we evaluate the applicability of the sensitivity function for four measurement modes, vertical and horizontal dipole modes with two coil separations. A field experiment compares EM38-MK2 measurements with a three-dimensional distribution of apparent electrical conductivity measured by time domain reflectometry (TDR). A positive linear correlation was obtained between the EM38-MK2 and TDR measurements. We found the sensitivity function to be applicable for the four measurement modes of the EM38-MK2. Comparison of EM38-MK2 data among the four different modes was able to identify the most saline layer from among five soil layers at depths of 0-20 cm, 20-50 cm, 50-75 cm, 75-150 cm, and 150+ cm. Our proposed method can provide useful information about underground salinity and will facilitate the resumption of farming in tsunami-damaged farmlands.