Combined first arrival, Rayleigh wave, and P-SV converted wave analysis for improved hydrologic characterization

We integrate vertically polarized P-SV converted bedrock refraction phase arrivals with first arrival and Rayleigh wave signals to estimate soil, fluid and rock properties at a shallow bedrock site near Crested Butte, CO. We validate our results with a synthetic elastic model. By combining the bedrock Vs refraction results with shallow Vs derived from Rayleigh wave inversion results, we obtain a composite Vs model that is integrated with our Vp model for hydrologic interpretation. The resulting analysis reveals zones of high Vp/Vs that we interpret as a perched aquifer setting within colluvium. The sediments overlie weathered and/or fractured shale. We suggest that P-SV phases are commonly observed in shallow bedrock seismic data and that robust bedrock Vs measurements can be obtained in environments where Vs-derived Rayleigh wave estimates may fail.