Cokriging Surface Topography and Seismic Refraction Data for Bedrock Topography

Our analysis of seismic refraction data collected at a proposed site of the Advanced Neutron Source (ANS) facility near Oak Ridge, Tennessee showed a strong correlation between surface and bedrock topography. By combining seismically determined bedrock elevation data with surface elevation data using cokriging, we were able to improve our map of bedrock topography significantly without collecting additional seismic data. In general, cokriging with surface elevation data as a secondary variable can improve estimates of bedrock elevation over those obtainable from seismic refraction alone, provided a good correlation exists between surface and bedrock topography. Our results indicate that simple linear regression performs nearly as well as cokriging when bedrock and surface topography are very highly correlated. However, cokriging is a more general approach, and produces error maps as a by-product that can be used to chose optimal locations for additional measurements.