REFLECTION AND LOVE-WAVE IMAGING OF A BURIED VALLEY USING 2D3C LAND-STREAMER SEISMIC DATA

We conduct reflection and Love-wave imaging on three two-dimensional (2D), three-component (3C) land-streamer seismic lines to characterize a buried bedrock valley underlying glacial deposits situated within southern Ontario, Canada. Understanding the valley’s characteristics is important for designing above-ground structures, investigating groundwater and surface water interactions, and erosion processes driven by glacial cycles. These characteristics include width, extension, overburden thickness, spatial facies distribution, and geometrical configuration of the overburden-bedrock contact. Reflection processing on the WSW-ENE trending profiles reveals the bedrock geometry and Quaternary sediment stratigraphy, including a shallow reflection associated with a lithostratigraphic transition zone. We utilize the dispersive properties of Love waves to derive pseudo-2D shear-wave velocity profiles along the seismic transects. The inversion process is constrained by the P-wave refraction velocities from reflection processing. We emphasize the significance of data preconditioning prior to surface wave analysis and propose an optimal processing sequence for moderately to highly noisy gathers. Likewise, we construct bedrock-reaching velocity profiles for depth conversion of reflectivity sections by using shear-wave velocity from Love-wave inversion, regression analysis, and water well data. The proposed signal preconditioning and integrated velocity modeling approach can be implemented in other areas where land-streamer seismic surveys are available, enhancing quantitative imaging and depth conversions. Blind borehole records demonstrate average depth-conversion errors of less than 2% following this approach. The Love-wave velocity imaging and the body-wave reflection imaging correlate well with each other and with lithological changes observed in water wells. This is demonstrated by the alignment of velocity contrasts with the geometry of the shallow reflection event at the lithostratigraphic transition zone. We find that the bedrock valley is approximately 60 m deep with a southward thinning width, possibly due to the valley’s geometry shifting from a north-south to an east-west orientation.