Ground penetrating radar: antenna frequencies and maximum probable depths of penetration in Quaternary sediments

Abstract

Ground penetrating radar (GPR) experiments were carried out in a gravel pit near Brigham City, Utah, USA,to determine maximum probable depths of penetration for 25, 50, 100 and 200 MHz antennas. We have found that this sedimentary field environment (quartzose-rich, thick, inclined gravel strata) is the most appropriate site known and available for the experimental objectives. With a 1000 V transmitter, 25 MHz antennas are capable of detecting stratigraphy to 52 m and possibly 57 m deep. Excessive signal losses for the 50, 100 and 200 MHz antennas occur at depths below 47, 37 and 28 m, respectively, preventing effective detection of stratigraphic interfaces. From 250 different field experiment sites, we suggest that these profiles represent the maximum probable GPR depths that can be confidently interpreted from any Quaternary unconsolidated sediments. A comparison of results shows a linear trend between different antenna frequencies and the maximum probable depth of penetration, suggesting that the 12.5 MHz antennas can detect strata to 66 m deep. Results obtained using the 25 MHz antennas indicate that at least 52 m of inclined strata, assumed to be foreset facies of gravel, occur beneath the gravel pit floor.