Improved GPR interpretation through resolution of lateral velocity heterogeneity: Example from an archaeological site investigation

In a typical common-offset ground-penetrating radar (GPR) survey, lateral velocity contrasts may go undetected leading to misinterpretation. Resolution of lateral velocity heterogeneity requires multi-fold acquisition and analysis. Further, pre-stack depth migration (PSDM) is required to produce accurate images in the presence of large lateral velocity gradients. In an archaeological investigation conducted near Boise, Idaho, we delineated a portion of what we interpret to be an abandoned dump site. Using multi-fold acquisition with reflection tomography, we identified an abrupt lateral velocity increase of ∼ 40% resulting in a substantial velocity pull-up in the time domain. PSDM corrected for the velocity pull-up enabling a more accurate interpretation and identification of additional structures of potential historical significance. The migration velocity model provided additional constraints on materials which enhanced our understanding of the subsurface.