Processing ground penetrating radar (GPR) data
Steven C. Fisher, Robert R. Stewart, Harry M. Jol
Two ground penetrating radar (GPR) profiles provided by the University of Calgary, Department of Geography are analyzed using seismic data processing techniques. The first is a 120m, 100 MHz, single-fold line from Ft. Smith, N.W.T. Processing operations performed on this data include signal saturation, gain recovery, spiking deconvolution, bandpass filtering, and normal moveout corrections. A failure surface with no surface expression is recognized in the final section. The second profile is a single-fold, 50 MHz, 0.5km line from William's Delta on Lake Athabaska, Saskatchewan, showing deltaic crossbed structures. These were processed using similar steps as above as well as f-k migration.
The filter bandwidths chosen from the 50 MHz and 100 MHz amplitude spectra were 20/30 - 70/100 MHz and 20/30 - 100/125 MHz respectively, suggesting very rapid attenuation of higher frequencies. A velocity spectrum was made for Williams Delta based on groundwave first arrivals and a common midpoint (CMP) gather velocity semblance analysis. Based on an average radar velocity of ~0.07m/ns, the William's Delta lithology was determined to be a water saturated fine sand. Analogous to seismic reflectivity, the GPR reflection coefficient is dependent on the dielectric contrast across an interface. Two higher velocity surface layer statics are recognized in the William's Delta profile. An attempt was made to correct these by flattening a water - table reflection. This was found to be insufficient, so a static correction formula was derived.