Multichannel Analysis of Surface Waves Generated During High-resolution Seismic Reflection Profiling of a Fluvial Aquifer

Abstract

Shear wave velocity profiles are estimated from surface wave dispersion analysis of data collected during a high-resolution P-wave reflection survey of a fluvial aquifer located in Columbus, Mississippi. The results demonstrate that useful velocity profiles of the upper [Formula: see text] of a sedimentary sequence can be imaged, even when survey design parameters and noise conditions are not optimal for surface wave surveys. The data were collected with [Formula: see text] geophones, a [Formula: see text] hammer source, and a [Formula: see text] geophone spacing with near and far offsets of 1 and [Formula: see text], respectively. In spite of these less-than-ideal survey parameters for surface wave analysis and the presence of substantial cultural noise arising from nearby quarrying operations and runway activity, the shear velocity profiles accurately locate the boundaries between a shallow soil layer and a meandering fluvial facies in the upper part of the aquifer, and the boundary between the meandering fluvial facies and a braided fluvial facies in the lower part of the aquifer. In general, shear velocities increase with increasing average grain size. Velocities average [Formula: see text] in the soil. In the meandering fluvial facies, velocities increase systematically with depth from [Formula: see text], and correlate with a systematic downward decrease in [Formula: see text] fraction in this upward fining sequence. In the braided fluvial facies, velocities decrease with depth from [Formula: see text], and correlate with a slight downward increase in [Formula: see text] fraction.