The effects of receiver arrangement on velocity analysis with multi‐concurrent receiver GPR data

Determining subsurface electromagnetic (EM) wave velocity is critical for ground-penetrating radar (GPR) data analysis, as velocity is used for the time-to-depth conversion, and hence leads to obtaining the precise location of the objects of interest. Currently, the way to acquire detailed subsurface EM wave velocity models involves employing multi-offset GPR surveys, such as wide-angle reflection-refraction (WARR), in conjunction with normal moveout (NMO) based velocity analysis. Traditionally, these surveys are carried out using two separate transducers and were, therefore, time-consuming and had limited uptake. Recent advances in GPR hardware have allowed the development of novel systems with multi-concurrent sampling receivers, which enable rapid and dense acquisition of WARR data. These additional receivers increase the overall size, weight and cost of the system. Therefore, we investigated the effects of receiver arrangement on NMO-based velocity analysis and considered reducing the overall number of transducers, whilst maintaining satisfactory velocity spectra resolution and, hence, obtaining detailed stacking velocity models as well as improved stacked reflection sections. We used both simulated data from complex three-dimensional models as well as field data and examined different numbers and positions of receivers in different environments. Our results show that velocity spectra resolution can be maintained within acceptable limits whilst reducing the number of receivers from a configuration with seven equally spaced receivers, to a sparse configuration of four receivers. Thus, being able to decrease the number of receivers used by these new GPR systems will reduce both the total system weight and cost and, hopefully, increase their adoption for GPR surveys.