Geophysical Methods for Stratigraphic Identification

Abstract

Although geophysics has been used for identifying subsurface fluid flow and contaminant spatial distributions at the Hanford Site and elsewhere, geophysics has not been generally used for identifying aquifer stratigraphy at environmentally relevant depths (> 70 m). This is because the bulk geophysical measurements of aquifer sediments cannot be directly related to sediment properties due to competing effects (e.g., porosity, pore-fluid conductivity, grain-sizes), thereby restricting the ability of conventional geophysical tools from discriminating their variation. Electrical resistivity tomography (ERT) is a method that can overcome these limitations because time-lapsed imaging, demonstrating changes in these properties over time, can be obtained from field sensors that can be left in place.