COMBINING SEISMIC REFLECTION AND RESISTIVITY PROFILING TO IMPROVE THE INTEPRETATION OF A BURIED VALLEY AQUIFER IN NORTHEAST ILLINOIS

Both high resolution seismic reflection and 2-D resistivity profiling have become fairly common tools for geologic mapping of Quaternary sediments. Seismic reflection profiling in shear-wave mode is not sensitive to variations in the degree of water saturation and is a valuable tool for mapping the geometry of buried valley aquifers and the composition of the valley-fill. Resistivity profiling, on the other hand, is more sensitive to bulk variations in facies changes and water saturation. We demonstrate the benefit of combining the two methods in the interpretation of a buried valley aquifer. Both seismic and resistivity data are acquired along the same line and processed independently. Then, the results of the seismic profile and borehole data are used as a primary model to constrain a new inversion of the resistivity profile. Interpretation is based on an overlay of the new resistivity profile on the seismic profile. Important subsurface features and variations in physical properties, which are not easily interpreted in either individual profile, become apparent in the combined profile.