A Comparison of Electrical Resistivity, Ground Penetrating Radar and Seismic Refraction Results at a River Terrace Site

Abstract

Electrical resistivity imaging (ERI), ground penetrating radar (GPR) and seismic refraction (SRF) profiles were repeated over three lines on a terrace of the Bow River. The site had a resistive gravel layer overlying mudstone bedrock with horizontal transitions to lacustrine and overbank deposits. Electrical resistivity results were best for determining changes in sediment types and detecting boundaries, but the ERI smoothness constraint blurred the location of the boundaries. The GPR gave the most resolution and showed internal structures that the other methods did not image. The GPR signal was severely attenuated in several areas where the surficial sediments became too conductive because of a fine grained component. The seismic refraction inversion provided good reproduction of the bedrock interface, but it did not detect changes in the composition of the surficial sediments. It also required the introduction of a low velocity surficial layer not indicated by the other methods that may be related to the increase in effective stress with depth. Jointly interpreting the three data sets gives a more reliable and less ambiguous interpretation than any single method. The data may be useful to test joint inversion algorithms and are available for download.