Target-oriented interferometric tomography for GPR data
Sherif M. Hanafy, Gerard T. Schuster, 2008. "Target-oriented interferometric tomography for GPR data", Seismic Interferometry: History and Present Status, Kees Wapenaar, Deyan Draganov, Johan O.A. Robertsson
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An interferometric form of Fermat’s principle and travel- time tomography is used to invert ground-penetrating radar (GPR) data for the subsurface velocity distribution. The input data consist of GPR traveltimes of reflections from two bur’ied interfaces, A (reference) and B (target), where the data are excited and recorded by GPR antennas at the surface. Fer- mat’s interferometric principle is then used to redatum the surface transmitters and receivers to interface A so the associ’ated reflection traveltimes correspond to localized transit times between interfaces A and B. The overburden velocity model above interface A is not required. The result after to- mographic inversion is a high-resolution estimate of the ve’locity between interfaces A and B that does not depend on the velocity model above interface A. A motivation for introduc’ing interferometric traveltime tomography is that typical lay’er-stripping approaches will see the slowness error increase with depth as the layers are inverted. This suggests that near- surface statics errors are propagated and amplified with depth. In contrast, the interferometric traveltime tomography method largely eliminates statics errors by taking the differ’ence between reflection events that emanate from neighbor’ing layer interfaces. Slowness errors are not amplified with depth. However, the method is sensitive to the estimation ac’curacy for the geometry of the reference interface. Both syn’thetic and real field data are used successfully to validate the effectiveness of this interferometric technique.