Comparing Vs profiles from MASW and downhole logging method from glacial deposits in central Illinois

We compared shear wave velocity (Vs) profiles from multichannel analysis of surface waves (MASW) to downhole Vs profiles measured in 10 boreholes in central Illinois to evaluate the reliability of the MASW Vs profiles measured in glacial deposits. The Vs profiles from the two methods were compared by calculating multiple statistical parameters, including average difference, average relative difference, relative standard deviation, and correlation coefficient resulting in overall average values of 71 m/s, 17 17 and 79 respectively. Such comparisons showed that the MASW-derived Vs profiles compare fairly well with Vs profiles acquired by downhole logging and that the MASW method provides reliable Vs measurements for mapping subsurface geology in the glacial deposits. We also used the data to investigate the effect of the rapid change in lithology with depth and the number of layers of the initial model input to MASW inversion on the reliability of the measured MASW Vs measurements. The lithologic heterogeneity did not have a significant effect on the MASW-derived Vs measurements. However, using an initial model input to MASW inversion with fewer number of layers has generally improved the accuracy of the MASW Vs measurements.