3D GROUND-PENETRATING RADAR (GPR) INVESTIGATIONS: BURIED CULVERTS, HISTORICAL GRAVES, A SANDSTONE RESERVOIR ANALOG, AND AN IMPACT CRATER

Ground-penetrating radar (GPR) is used to characterize a variety of subsurface targets such as buried culverts, historical graves, reservoir analogs, and impact craters. In the first case of “buried culverts” I evaluated the GPR performance across five antenna frequencies to determine which would best image buried culverts. Laboratory measurements of soil were made to provide independent measurements to compare measurements and estimates from the field experiments and other sources. Estimates of radar velocities for the set of GPR antenna frequencies were made by a variety of GPR processing techniques together with survey measurements. These velocities were then used in the imaging and time-to-depth conversion of the GPR data. The best velocity used for the various migrations showed a frequency dependence. In the second case of “historical graves” Terrestrial Laser Scanning (TLS) was used before GPR to provide an elevation map of the survey area. This map was analyzed to find anomalous mounds and depressions which provided leads to the location of undocumented graves that could be surveyed in depth with GPR for verification. In the third case of “reservoir analogs” I used 3D GPR to visualize the internal structure of terminal distributary mouth bars in the Cretaceous Ferron Sandstone in southeastern Utah. Three radar facies were observed including a terminal distributary channel of 1.25 m thickness filled with distributary mouth bars, a progradational mouth bar with a dip angle of approximately 20o, and a laterally continuous basal planar bed. GPR images revealed the geometry of architectural elements such as small-scale bedding (0.6 m) and the extent (9 m) of major bounding surfaces. In the fourth case of “craters” I used 3D GPR to image ejecta elements and to map the alluvium thickness at the Barringer (Meteor) Crater in Arizona. Some software was developed to assist the processing. Workflows were developed for TLS data and 3D GPR data. The results for all four cases were interpreted successfully and recommendations for future acquisition, processing, and interpretation were compiled. The wide range of imaging cases shows the usefulness of GPR in the imaging of buried culverts, historical graves, reservoir analogs, and impact craters.