Seismic refraction methodology for groundwater level determination: "Water seismic index"

Recently, there has been increased interest in the use of refraction seismic data for the exploration and development of hydrological reservoirs. The aim of this study is to provide a procedure in order to identify groundwater levels by means of seismic refraction profiles. Assuming that the velocity of shear waves increases much less than the velocity of compressional waves in a saturated soil, seismic refraction surveys were performed for the determination of the water table. In order to have a perfect overlay of the tomography 2D grids, P and S wave seismic profiles were obtained with the same geometrical configuration. Based on the propagation of the P and S waves in the unsaturated and saturated media, a "Water Seismic Index" (WSI) was defined. WSI is related to the local variations of the P and S wave velocities and, in theoretical terms, it is correlated to groundwater level. Preliminary results indicate that there is a good agreement between the depth of the ground water and the WSI parameter.